Method and apparatus for evaluating electrostatic or nonlinear devices

ABSTRACT

Aspects are directed to a MEMS device configurable to receive signals from a first, a second, a third, and a fourth signal source operating at a first, a second, a third, and a fourth frequency, respectively. The MEMS device may be configured to combine the first signal with the second signal generating a first combined signal, and to combine the third signal with the fourth signal generating a second combined signal. The first combined signal may be coupled to the first terminal of the MEMS device while the second combined signal may be coupled to the second terminal of the MEMS device. The first common terminal may be configured to produce an output associated with the second and fourth frequencies. The MEMS device may be further configured to derive from the produced output a signal indicative of nonlinearities or of changes in capacitance related to the MEMS device.

OVERVIEW

Aspects of various embodiments are directed to evaluating or measuringthe position of a Micro-ElectroMechanical System (MEMS) device (e.g., anelectrostatic microactuator) in terms of phase and or amplitudecharacteristics.

MEMS devices are useful for a variety of applications. However, ensuringproper operation of such devices is both important and challenging. Forinstance, lock-in amplifiers have been used to measure substantiallylinear displacements of the MEMS device. Various other approaches forassessing MEMS devices have been utilized, yet have been limited intheir ability to assess specific components therein.

These and other matters have presented challenges to efficacies andefficiencies of MEMS implementations, for a variety of applications.

SUMMARY

According to certain embodiments, aspects of the present disclosureinvolve measuring the characteristics of a MEMS device (e.g., anelectrostatic microactuator) to provide information related to how thedevice would behave under certain operating conditions. One exampleembodiment is directed to examining or measuring each of the MEMS-typeelements (e.g., independently) in terms of motion, position, orcapacitance. For example, each of the elements (e.g., electrodes) of aMEMS device may be measured independently.

Various example embodiments are directed to issues such as thoseaddressed above and/or others which may become apparent from thefollowing disclosure concerning MEMS devices.

In another specific example embodiment, an apparatus includes a MEMSdevice as well as filtering and processing circuitry. The MEMS deviceincludes mechanical, electro-mechanical, and a capacitive sectionsincluding a first terminal, a second terminal and a common terminal. Theterminals are collectively configured to provide electrical-signalstimulation at the first terminal and the second terminal by providingan output signal at the common terminal. The filtering and processingcircuitry is configured and arranged to process information derived fromthe output signal at the common terminal, and generate therefrom asignal indicative of changes in capacitance related to at least one ofthe first and second terminals of the MEMS device. Such first and secondterminals may form part of a capacitor or capacitive structure(element/circuit), and a common terminal may be located sufficientlybetween the first and second terminals.

A particular embodiment is directed to a MEMS apparatus including amechanical component configured and arranged to actuate in response toan input signal, and circuitry configured and arranged to actuate themechanical component by modulating the input signal via signalmodulation. The signal modulation may be selected from the group of:drive amplitude modulation, phase modulation, frequency modulation, anda combination thereof. Further circuitry is configured and arranged todetermine an angular and linear position of the mechanical componentbased on the phase of the input signal.

Another embodiment is directed to an apparatus including a MEMS devicehaving mechanical, electro-mechanical, and capacitive portions, andfurther including a first terminal, a second terminal, and a firstcommon terminal. The apparatus also includes signal sources, including afirst signal source configured and arranged to operate at a firstfrequency and to output a first signal, a second signal sourceconfigured and arranged to operate at a second frequency and to output asecond signal, wherein the first frequency is lower than the secondfrequency, a third signal source configured and arranged to operate at athird frequency and to output a third signal, and a fourth signal sourceconfigured and arranged to operate at a fourth frequency and to output afourth signal, wherein the third frequency is lower than the fourthfrequency. The apparatus includes further circuitry configured andarranged to combine the first signal with the second signal to form afirst combined signal, wherein the first combined signal is coupled tothe first terminal of the MEMS device, as well as circuitry configuredand arranged to combine the third signal with the fourth signal to forma second combined signal, wherein the second combined signal is coupledto the second terminal of the MEMS device. The first common terminal isconfigured to produce an output respectively associated with the secondand fourth frequencies. The apparatus also includes filtering andprocessing circuitry configured and arranged to filter and processinformation derived from the produced output and generate therefrom asignal indicative of changes in capacitance related to the secondterminal of the MEMS device.

The above discussion/summary is not intended to describe each embodimentor every implementation of the present disclosure. The figures anddetailed description that follow also exemplify various embodiments.

BRIEF DESCRIPTION OF FIGURES

Various example embodiments may be more completely understood inconsideration of the following detailed description in connection withthe accompanying drawings, in which:

FIG. 1 depicts circuitry including two or more signal sources, inaccordance with the present disclosure;

FIG. 2 depicts circuitry including two or more signal sources, inaccordance with the present disclosure;

FIG. 3 depicts circuitry utilizing two or more signals with at least twodifferent phases, in accordance with the present disclosure;

FIG. 4 depicts circuitry using two or more signals with at least twodifferent phases, in accordance with the present disclosure;

FIG. 5 illustrates an exemplary multi-dimensional device, in accordancewith the present disclosure;

FIG. 6 depicts detection and demodulation circuitry that can be used torecover a signal or signals from the output of amplifier and/or filtercircuitry, in accordance with the present disclosure;

FIG. 7 depicts filter circuitry, in accordance with the presentdisclosure;

FIG. 8 depicts measurement circuitry including multiple carrier signalsources, in accordance with the present disclosure;

FIG. 9 depicts exemplary filter circuitry including measuring circuitry,in accordance with the present disclosure;

FIG. 10 illustrates a feedback system, in accordance with the presentdisclosure;

FIG. 11 depicts exemplary quadrature (IQ) modulation and detectioncircuitry, in accordance with the present disclosure;

FIG. 12 depicts exemplary demodulation, detection, and filteringcircuitry, in accordance with the present disclosure;

FIG. 4A shows a high frequency signal demodulator that is coupled tomultiple filters (e.g., a filter bank) and multiple phase demodulatorsand multiple amplitude (e.g., AM, amplitude modulation) demodulators, inaccordance with the present disclosure;

FIG. 5A shows a distorted signal from the output of the HF BPF AMP block104 from FIG. 4A, in accordance with the present disclosure;

FIG. 6A shows an example circuit of block 104 from FIG. 4A, inaccordance with the present disclosure;

FIG. 7A shows an example filter circuit for blocks 105, 106, and or 107from FIG. 4A, and an example circuit including a detector/demodulatorand filter circuit for blocks 108, 109, and or 110 from FIG. 4A, inaccordance with the present disclosure;

FIG. 8A shows an example phase detector circuit for blocks 111, 112, andor 113 from FIG. 4A, in accordance with the present disclosure;

FIG. 9A shows phase detection for providing an accurate method orapparatus to adjust an oscillator to the precise frequency of resonanceof a MEMS device, in accordance with the present disclosure; and

FIG. 10A shows a MEMS device including sub-mode(s), or wherein the MEMSdevice has at least one other frequency of resonance, in accordance withthe present disclosure.

While various embodiments discussed herein are amenable to modificationsand alternative forms, aspects thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the disclosureto the particular embodiments described. On the contrary, the intentionis to cover all modifications, equivalents, and alternatives fallingwithin the scope of the disclosure including aspects defined in theclaims. In addition, the term “example” as used throughout thisapplication is only by way of illustration, and not limitation.

DETAILED DESCRIPTION

Aspects of the present disclosure are believed to be applicable to avariety of different types of apparatuses, systems and methods involvingMicro-Electro Mechanical System (MEMS) components. In certainimplementations, aspects of the present disclosure have been shown to bebeneficial when used in the context of a MEMS device and approachinvolving measurement and/or utilization of capacitance or motionalchanges therein. Certain aspects are directed to such implementationsusing a common signal electrode. In some embodiments, frequency divisionmultiplexing and quadrature signal processing techniques are utilized tofacilitate measuring individual portions of a MEMS device. Filter banksmay be included to provide real-time analysis of phase and amplitude offundamental frequency and distortion products. Such approaches mayfacilitate testing/measuring of individual electrodes within MEMSdevices. While not necessarily so limited, various aspects may beappreciated through the following discussion of non-limiting exampleswhich use exemplary contexts.

Accordingly, in the following description various specific details areset forth to describe specific examples presented herein. It should beapparent to one skilled in the art, however, that one or more otherexamples and/or variations of these examples may be practiced withoutall the specific details given below. In other instances, well knownfeatures have not been described in detail so as not to obscure thedescription of the examples herein. For ease of illustration, the samereference numerals may be used in different diagrams to refer to thesame elements or additional instances of the same element. Also,although aspects and features may in some cases be described inindividual figures, it will be appreciated that features from one figureor embodiment can be combined with features of another figure orembodiment even though the combination is not explicitly shown orexplicitly described as a combination.

Various aspects of the disclosure are directed to an apparatus includinga MEMS device as well as filtering and processing circuitry. The MEMSdevice includes mechanical, electro-mechanical, and a capacitivesections including a first terminal, a second terminal and a commonterminal. The terminals are collectively configured to provideelectrical-signal stimulation at the first terminal and the secondterminal by providing an output signal at the common terminal. Thefiltering and processing circuitry filters and processes informationderived from the output signal at the common terminal, and generatestherefrom a signal indicative of changes in capacitance related to atleast one of the first and second terminals of the MEMS device.

The output signal at the common terminal can be generated or provided ina variety of manners. In some implementations, the output signal isindicative of a nonlinearity associated with the capacitive section. Inother implementations, the output signal is indicative of a nonlinearityassociated with the capacitive section, with the MEMS device beingconfigured to respond to changes in amplitudes of or phases associatedwith the electrical-signal stimulation at the first terminal and thesecond terminal, and therein to cause accentuation of changes incapacitance as indicated in the generated signal.

In certain embodiments, the MEMS device includes micromirrors coupled toor as part of the MEMS device, wherein resonance associated with themicromirrors or the MEMS device is configured as a function of theoutput signal. In some implementations, the MEMS device is configured toincrease a field of view provided by the micromirrors by at least twoorders of magnitude, to facilitate the micromirrors being driven at aselected frequency, and to facilitate drive voltages for the MEMS deviceto be modulated in amplitude, phase, and/or frequency for optimized scanpatterns.

Embodiments involving micromirrors may be utilized in a variety ofapplications. In some embodiments, micromirrors coupled to or as part ofthe MEMS device are utilized in an apparatus including or referring to aLIDAR device in which the micromirrors are used in a LIDAR or lasermicroscopy application. In other embodiments, micromirrors coupled to oras part of a MEMS device and an apparatus that includes or refers to aheads-up or mounted display in which the micromirrors are used forproviding images in the heads-up or mounted display.

In accordance with various embodiments, aspects of the presentdisclosure are directed to a MEMS device including mechanical,electro-mechanical, and capacitive portions, and a first terminal, asecond terminal, and a first common terminal. Such first and secondterminals may form part of a capacitor or capacitive structure(element/circuit), and a common terminal may be located sufficientlybetween the first and second terminals. A first signal source can beconfigured and arranged to operate at a first frequency and to output afirst signal. A second signal source can be configured and arranged tooperate at a second frequency and to output a second signal. The firstfrequency is lower than the second frequency. A third signal source canbe configured and arranged to operate at a third frequency and to outputa third signal. A fourth signal source can be configured and arranged tooperate at a fourth frequency and to output a fourth signal. The thirdfrequency is lower than the fourth frequency. Circuitry included in theMEMS device can be configured and arranged to combine the first signalwith the second signal to form a first combined signal. The firstcombined signal is coupled to the first terminal of the MEMS device. TheMEMS device may include circuitry configured and arranged to combine thethird signal with the fourth signal to form a second combined signal.The second combined signal is coupled to the second terminal of the MEMSdevice. The first common terminal included in the MEMS device can beconfigured and arranged to produce an output respectively associatedwith the second and fourth frequencies. The MEMS device may furtherinclude filtering and processing circuitry configured and arranged tofilter and process information derived from the produced output, and togenerate therefrom a signal indicative of changes in capacitance relatedto the second terminal of the MEMS device. In some embodiments, theprocessing circuitry is configured to detect the amplitude and/or phaseof a signal being processed.

In accordance with a particular embodiment, an apparatus utilizesmodulation of drive amplitude, phase, or/and frequency of a signalapplied for actuating a mechanical component, while using a phasemonitor to determine the angular and linear position of the mechanicalcomponent in real time. In various implementations, the mechanicalcomponent includes one or more micromirrors. In a particular suchembodiment, micromirrors are used on resonance in a manner thatincreases their field of view by two orders of magnitude or more, allowsthe micromirrors to be driven at high frequency to improve the speed ofthe systems in which they are deployed, and allows the drive voltages tobe modulated in amplitude, phase, and frequency for desired scanpatterns. These approaches are useful for micromirrors in a variety ofapplications, such as LIDAR, laser microscopy, and head-mounteddisplays.

Accordingly, such a micromirror approach may be implemented with theabove-mentioned MEMS device including mechanical, electro-mechanical,and capacitive portions, along with the respective terminals. In thiscontext, the mechanical portion includes a micromirror and the circuitrythat is configured to detect the phase of the signal being processed isfurther configured to determine an angular and linear position of themicromirror while the micromirror is driven by a signal exhibitingmodulation. Such modulation may include one or more of drive amplitudemodulation, phase modulation, frequency modulation, and a combinationthereof.

A more particular embodiment is directed to a MEMS apparatus including amechanical component configured and arranged to actuate in response toan input signal, and circuitry configured and arranged to actuate themechanical component by modulating the input signal via signalmodulation. The signal modulation may be selected from the group of:drive amplitude modulation, phase modulation, frequency modulation, anda combination thereof. Further circuitry is configured and arranged todetermine an angular and linear position of the mechanical componentbased on the phase of the input signal.

Turning now to the figures, it is noted that various common referencenumerals are utilized in different figures to refer to differentcomponents. In this context, the reference numerals pertain to thosecomponents in the figure with which the reference numerals are utilized.While certain such componentry may also be implemented similarly fromfigure to figure, and while aspects of different figures may be utilizedseparately or combined, the instant disclosure is not limited as such.

FIG. 1 depicts an example apparatus, in accordance with the presentdisclosure in which MEMS device C1 includes mechanical,electro-mechanical, and capacitive portions. A first signal source (notshown) can configured and arranged to operate at a first frequency andoutput a first signal, Vm. A second signal source (not shown) can beconfigured and arranged to operate at a second frequency and to output asecond signal, VRF1. The frequency of the first signal, Vm, is lowerthan the frequency of the second signal, VRF1. A third signal source(not shown) can be configured and arranged to operate at a thirdfrequency and to output a third signal, Vm\. A fourth signal source canbe configured and arranged to operate at a fourth frequency and tooutput a fourth signal, VRF2. The frequency of the third signal, Vm\, islower than the frequency of the fourth signal, VRF2.

Also depicted in FIG. 1 is S1, which is circuitry and/or a function forcombining (e.g., an adder) the first signal, Vm, with the second signal,VRF1, to form a first combined signal. The first combined signal iscoupled to the first terminal 202 of the MEMS device C1. Similarly, S2is circuitry and/or a function for combining (e.g., an adder) the thirdsignal, Vm\, with the fourth signal, VRF2 to form a second combinedsignal. The second combined signal is coupled to the second terminal 203of the MEMS device C1. First common terminal 201 can be configuredbetween, or sufficiently proximate the adjacent terminals of thecapacitor (or capacitive portion of the MEMS device), to produce anoutput respectively associated with the second frequency, that of thesignal VRF1, and the fourth frequency, that of VRF2. Signals Vm and Vm\can be push/pull, differential, or complementary phase signals whosefrequencies can be the same as or different from each other.

Filtering and processing circuitry 205 can be configured and arranged tofilter and process information derived from the produced output andgenerate therefrom a signal indicative of changes in capacitance relatedto the second terminal 203 of the MEMS device C1. However, if the outputsignal produced by the first common terminal 201 is a small signal,optionally included amplifier circuitry 204 amplifies the producedoutput signal before it is further processed by filtering and processingcircuitry 205. Filtering and processing circuitry 205 then outputssignals Vdet_A and Vdet_B.

Expounding upon FIG. 1 by using a related but more-specificallycharacterized block diagram and also to the present disclosure directed,FIG. 2 depicts an embodiment with aspects to a MEMS device receivingfirst signal Vm, second signal VRF1, third signal Vm\, and fourth signalVRF2. Furthermore, Vm and Vm\ are modulating signals, as they providedeflection and/or rotation within MEMS device C1. Signals Vm and Vm\ canbe push/pull, differential, or complementary phase signals whosefrequencies can be the same as or different from each other.

In some embodiments, the frequencies of Vm and Vm\ are less than 200kHz, thus creating movement and/or deflection of MEMS device C1.Frequencies values of VRF1 and VRF2 are typically higher than those ofVm and Vm\. In various related embodiments, carrier frequencies may bein the 1 to 2 MHz range, or could be lower or higher such as 200 kHz to500 kHz, or 2 MHz to 20 MHz. These and various other related embodimentsmay be directed toward insuring a low impedance input to negate staycapacitances from wiring, with a carrier frequency of <10% of that (800MHz or lower). Generally, higher frequencies associated with VRF1 andVRF2 are different from one another, and preclude movement in the MEMSdevice C1. For instance, if the frequencies of VRF1 and/or VRF2 are >1MHz, VRF1 and/or VRF2 will not be able to cause movement (e.g.,vibration, rotation, etc.) in mechanical, electro-mechanical, and/orcapacitive elements of the MEMS device C1 because the MEMS device C1 hasa mass that cannot respond to a 1 MHz signal, as such a frequency is toohigh. The frequencies of Vm, Vm\, VRF1, and VRF2 can assume othervalues, and are not strictly limited to any values or ranges providedherein.

Applying the first combined signal (the result of combining signals Vmand VRF1 at combining circuitry S1) to the first terminal 502 of theMEMS device C1 generates a measurable capacitance across the firstterminal 502 and the first common terminal 501. The second terminal 503of the MEMS device C1 has applied the second combined signal, which isthe result of combining signals Vm\ and VRF2 at combining circuitry S2.Application of the second combined signal to the second terminal 503generates a measureable capacitance across the second terminal 503 andthe first common terminal 501. Signals Vm and Vm\ can have the samefrequency, and can be used to modulate (e.g., induce mechanical movementin the form of vibration, rotation, etc.) in the MEMS device C1.

The capacitance across first terminal 502 and the first common terminal501 and/or the capacitance across the second terminal 503 and the firstcommon terminal 501 can be measured independently via amplifiercircuitry 504 with bandpass filters 516 and 517. Typically, bandpassfilter 516 can be configured and arranged to pass a set of frequenciesrelated to VRF1 while attenuating signals related to VRF2. Additionallyand/or alternatively, bandpass filter 517 can be configured and arrangedto pass a set of frequencies related to VRF2 while attenuating signalsrelated to VRF1.

Signals output by the bandpass filters 516 and 517 are coupled todetector circuitry (e.g., detectors) 526 and 527. The signals output bydetectors 526 and 527 are Vdet_A which provides a signal indicative ofthe capacitance across the first terminal 502 and the first commonterminal 501, and Vdet_B which provides a signal indicative of thecapacitance across the second terminal 503 and the first common terminal501. Signal Vm changes (e.g., modulates) the measurable capacitance ofthe MEMS device C1 between the first terminal 502 and the first commonterminal 501, and signal Vm\ changes (e.g., modulates) the measurablecapacitance of the MEMS device C1 between the second terminal 503 andthe first common terminal 501. Typically, when signal Vm is combined atcombining circuitry Si with higher frequency VRF1 such that when thecapacitance of the MEMS device C1 as measured across the first terminal502 and the first common terminal 501 is modulated by varying signal Vm,the signal current in the first common terminal 501 is an amplitudemodulated signal that is coupled to an input terminal of amplifiercircuitry 504. Similarly, when signal Vm\ is combined at combiningcircuitry S2 with higher frequency VRF2 such that when the capacitanceof the MEMS device C1 as measured across the second terminal 503 and thefirst common terminal 501 is modulated by varying signal Vm\, the signalcurrent in the first common terminal 501 is an amplitude modulatedsignal that is coupled to an input terminal of amplifier circuitry 504.The signal output by amplifier circuitry 504 includes at least twoamplitude modulated signals, typically at different carrier frequencies,such that bandpass filters 516 and 517 pass one carrier frequency andnot the other. In some embodiments in accordance with the presentdisclosure, detectors 526 and 527 can include an amplitude modulationdetector and/or amplitude modulation demodulator. Such amplitudemodulation detection/demodulation circuitry can include an envelopedetector or a synchronous detector.

The bandpass filters 516 and 517 and/or the detectors 526 and 527depicted in FIG. 2 can include a scaling factor. The scaling factor canbe dependent on one or more frequencies of VRF1 and VRF2. If the valueof VRF1 is f1 and the frequency of VRF2 is f2, then the scaling factorequals f1/f2 for the bandpass filter 517 or the detector 527. Forexample, if f1=1 MHz and f2=2 MHz, then the center frequency of thebandpass filter 516 is 1 MHz and the center frequency of the bandpassfilter 517 is 2 MHz. Given the same measured capacitance, at 2 MHz thecapacitor current in the first common terminal 501 of the MEMS device C1will be double the capacitor current at 1 MHz. As another example, whenthe signals Vm and Vm\ are zero, the capacitance measured across thefirst terminal 502 and the first common terminal 501 equals thecapacitance measured across the second terminal 503 and the first commonterminal 501. Therefore, applying a scale factor of 50% (1 MHz/2MHz=0.5, or 50%) to the bandpass filter 517 and/or the detector 527 willreduce the produced output signal by 50%. In turn, this will match thesignal gain from the bandpass filter 516 and the detector 526.

Additional embodiments of the present disclosure directed coupling theoutput terminals and/or signals Vdet_A and Vdet_B of detectors 526 and527 to a differential amplifier, difference amplifier, transformer, ordifferencing function to provide a difference signal derived from Vdet_Aand Vdet_B. This difference signal provides a signal indicative of a net(combined) movement or position of a rotor or plates of the MEMS deviceC1 (e.g., an electrostatic microactuator).

Amplifier circuitry 504 can include a transimpedance amplifier and/or atransresistance amplifier including a low impedance/resistance load tothe first common terminal 501. Coupling the first common terminal 501 toa low impedance/resistance amplifier can decrease sensitivity to stray(e.g., parasitic) capacitance from wiring resulting in more accuratemeasurements of the signal current provided by the first common terminal501.

Depicted in FIG. 3 is a MEMS device C1 receiving phase-shifted (e.g.,quadrature) signals VI and VQ. In various embodiments, the frequency ofVI can be equal to the frequency of signal VQ, and the difference inphase between signals VI and VQ can be +/−90 degrees. The frequency ofmodulating signals Vm and Vm\ is lower than the frequency of VI and VQ,and VI and/or VQ can be one or more carrier signals. Additionally and/oralternatively, VI and/or VQ can be one or more higher frequency signals.For example, VI can include a cosine waveform and VQ can include a sinewaveform. The MEMS device (e.g., an electrostatic microactuator) C1depicted in FIG. 3 can be coupled to lower frequency signals Vm and Vm\.Signals Vm and Vm\ can be push/pull or differential signals. Higherfrequency signal VI is combined with Vm at combining circuitry 51. Theoutput of the combining circuitry 51 is coupled to the first terminal502 of the MEMS device C1. Higher frequency signal VQ is combined withVM\ at combining circuitry S2, the output of which is coupled to thesecond terminal 503 of the MEMS device C1. The first common terminal 501is coupled to amplifier circuitry 504, the output of which is coupled tobandpass filter 505. Bandpass filter 505 passes signals related to thefrequency of VI and/or VQ, and outputs signal Vout 505. The signaloutput Vout 505 by the bandpass filter 505 is input to amplitudedetection/demodulation circuitry 508 and phase detection/demodulationcircuitry 509. The amplitude detection/demodulation circuitry 508outputs signal Vdet2 p″, which is a signal indicative of movement (e.g.,the position of) the MEMS device C1. The phase detection/demodulationcircuitry 509 includes reference signal Vref0, which includes a signalrelated to VI and/or VQ that can or cannot be phase shifted. Referencesignal Vref0 is coupled to input terminal, InA, of the phasedetection/demodulation circuitry 509. The output signal of the bandpassfilter 505, Vout505, is coupled to the phase detection/demodulationcircuitry 509 at input terminal InB. Signal Vref0 can have a phase suchthat it provides demodulation of both signals related to VI and VQ. Forexample, the phase angle of Vref0 can be such that it is an anglehalfway between the phase angles of VI and VQ. Output signal Vout505 caninclude an amplitude modulates signal and/or a phase modulated signal.Amplitude detection/demodulation circuitry 508 outputs signal Vdet2 p″which is indicative of motion or the position of a portion of the MEMSdevice C1. Phase detection/demodulation circuitry 509 outputs a signal,Vdet1 p″, which is indicative of motion or the position of a portion ofthe MEMS device C1.

FIG. 4 depicts quadrature signals (signals having a phase difference of+/−90 degrees) VI and VQ, which can be used to measure portions of theMEMS device C1. The signal VI provides an ‘in-phase’ signal, while thesignal VQ provides a ‘quadrature’ signal. Combining circuitry S1combines (e.g., adds) signals Vm and VI. The output of the combiningcircuitry S1 is input to the first terminal 502 of the MEMS device C1.Combining circuitry S2 combines (e.g., adds) signals Vm\ and VQ, andoutputs a signal that is coupled to the second terminal 503 of the MEMSdevice C1. The first common electrode 501 of the MEMS device C1 providesa signal that is input to filter circuitry 504. In specific embodiments,Vm and Vm\ can have the same frequency, as can the signals VI and VQ. Insuch instances, the frequency of Vm and Vm\ is lower than the frequencyof VI and VQ.

A first combined signal at the first common terminal 501 provides amodulated (e.g., in terms of amplitude or phase) signal via modulatingsignal Vm with an in-phase angle (e.g., 0 [zero] degrees). Additionallyand/or alternatively, the first common terminal 501 provides a modulated(e.g., in terms of amplitude or phase) signal via modulating signal Vm\with a quadrature phase angle (e.g., 90 degrees). Amplifier circuitry504 outputs an amplified signal that is input to bandpass filter 505.Bandpass filter 505 passes signals according to the frequency of VIand/or VQ. Synchronous detectors 506 and 507 provide demodulation of thesignal output by bandpass filter 505, using reference signal Vref1 andVref2. The frequency of Vref1 is the same as VI. The frequency of Vref2is the same as VQ. Typically, the frequency of VI is the same as thefrequency of VQ. In some embodiments, the phase of Vref1 can be eitherthe same or the inverse of the phase of VI, while the phase of Vref2 canbe either the same or the inverse of the phase of VQ. In variousembodiments, the signals Vref1 and Vref2 can be in quadrature (e.g., thesignals are 90 degrees out of phase).

By providing demodulation of quadrature signals, the synchronousdetectors 506 and 507 can measure capacitive changes and/or movements ofthe MEMS device C1. For instance, the capacitance across the firstterminal 502 and the first common terminal 501 of the MEMS device C1 canbe measured separately/independently of the capacitance across thesecond terminal 503 and the first common terminal 501 of the MEMS deviceC1. The synchronous detectors 506 and 507 can include a low pass filterwhich attenuates the output signal of the synchronous detectors 506 and507 according to the frequencies of the signals VI and VQ. For example,synchronous detector 506 outputs signal Vdet2 p which is indicative ofthe capacitance and/or movement measured across the first input terminal502 and the first common terminal 501 of the MEMS device C1.Additionally and/or alternatively, synchronous detector 507 outputssignal Vdet1 p which is indicative of the capacitance and/or movementmeasured across the second input terminal 503 and the first commonterminal 501 of the MEMS device C1.

Synchronous detector 506, as depicted in FIG. 4, can include a firstinput terminal coupled to the first reference signal, Vref1, related tosignal VI. Synchronous detector 506 can further include a second inputterminal coupled to an output signal (e.g., Vout505) of bandpass filter505. Similarly, synchronous detector 507, as depicted in FIG. 4, caninclude a first input terminal coupled to a first reference signal,Vref2, related to the signal VQ. Synchronous detector 507 can furtherinclude a second input terminal coupled to an output signal (e.g.,Vout505) of bandpass filter 505. Synchronous detectors 506 and 507 caninclude circuitry for multiplying (e.g., multiplier circuitry) thesignals received as inputs in order to generate their respective outputsignals (e.g., Vdet2 p and Vdet1 p, respectively). Additionally and/oralternatively, synchronous detectors 506 and 507 can include phasedetection circuitry and/or filter circuitry to provide modulation and/ordemodulation (e.g., in terms of amplitude or phase) of the signals beingprocessed by synchronous detectors 506 and 507. Synchronous detectors506 and 507 can be realized through analog or digital means.

If, for example, Vout505 as depicted in FIG. 4 is an amplitudemodulated, quadrature signal, it will have the form of:Vout505=[1+m₅₀₂(t)][cos(ωct)]+[1+m₅₀₃(t)][sin(ω_(c)t)], where m₅₀₂ canbe thought of as the movement (e.g., deflection) and/or capacitancemeasured across the first terminal 502 and the first common terminal 501of the MEMS device C1 over time, and where m₅₀₃ can be thought of as themovement (e.g., deflection) and/or the capacitance measured across thesecond terminal 503 and the first common terminal 501 of the MEMS deviceC1 over time. To demodulate this signal, it can be assumed:Vref1=cos(ω_(c)t) at synchronous detector 506, Vref2=sin(ω_(c)t) atsynchronous detector 507.

In various contexts, ω_(c)=2πf_(c), where f_(c) is the carrierfrequency, or as in these particular embodiments, f_(c) is the frequencyof VI and/or VQ. Referring to synchronous detector 506, which carriesout multiplication for demodulation (e.g., prior to output filtering),Vdet2 p=cos(ω_(c)t)×Vout505, whereby an output (e.g., low pass) filteris included to provide a signal related to m₅₀₂(t) and remove signalsrelated to f_(c). Referring synchronous detector 507, which carries outmultiplication for demodulation, Vdet1 p=sin(ω_(c)t)×Vout505 wherebyanother output (e.g., low pass) filter is included to provide a signalrelated to m₅₀₃(t) and remove signals related to f_(c). There is a 90degree phase shift between Vref1 and Vref2 (e.g., via cosine and sinefunctions, cos(ω_(c)t) and sin(ω_(c)t)). Synchronous detectors 506 and507 may include a filtering component such as low pass filtering toremove signals related to f_(c) (e.g., the frequency of VI and/or VQ).Additionally and/or alternatively, synchronous detectors 506 and 507 caninclude filtering circuitry/functionality such as to effect high passfiltering in order to remove signals related to 0 Hz or around 0 Hz.

FIG. 5 depicts a device including a vertical axis (y-axis) andhorizontal axis (x-axis), herein defined as a multi-dimensional device(e.g., the MEMS device C1). Embodiments of the present disclosure aredirected to multi-dimensional devices for the projection and/or thedisplay of an image. In specific embodiments, the mechanical,electro-mechanical, and/or capacitive portions of the multi-dimensionaldevice can be measured separately/independently. For instance, themovement (e.g., displacement) and/or capacitance across the firstterminal 502 and the first common terminal 501″ of the MEMS device C1″can be measured. Similarly, the movement (e.g., displacement) and/orcapacitance across the second terminal 503 and the first common terminal501″ of the MEMS device C1″ can be measured. These measurements can betaken independently of one another. The first common terminal of theMEMS device C1″ outputs a signal that is input to amplifier circuitry504.

As a specific example and using FIG. 5 as reference, the (higher)frequencies for the signals VRF1, VRF2, VRF3, and VRF4 may includecos(ω₁t+φ₁), cos(ω₂t+φ₂), cos(ω₃t+φ₃), and cos(ω₄t+φ₄), where ω₁, ω₂,ω₃, and ω₄ are frequencies in radians per second and where in generalω=2πf, where f=frequency in Hz; and whereby φ₁, φ₂, φ₃, and φ₄ representphase shift or phase angle(s). Also, ω₁=2πf₁, ω₂=2πf₂, ω₃=2πf₃, andω₄=2πf₄. For a frequency division multiplex example embodiment, thehigher (e.g., carrier) frequencies f₁, f₂, f₃, and f₄ are different.Signals Vm and Vm\, used for modulation/deflection, can be push/pull,differential, or complementary signals having the same frequency, afrequency which is less than the value of f₁, f₂, f₃, and f₄. SignalsVm2 and Vm2\, used for modulation/deflection, can be push/pull,differential, or complementary signals having the same frequency, afrequency which is less than the value of f₁, f₂, f₃, and f₄. Inspecific embodiments, the signals Vm, Vm2, Vm\, and Vm2\ can have thesame frequency, while in other embodiments, the frequency of the signalsVm, Vm2, Vm\, and Vm2\ can be different.

As depicted in FIG. 5, the MEMS device C1″ can include a first terminal502, a second terminal 503, a third terminal 505, a fourth terminal 506,and a first common terminal 501″. Combining circuitry Si combines (e.g.,adds) the signal Vm with a higher frequency reference signal, VRF1, andoutputs a signal that is coupled to the first terminal 502 of the MEMSdevice C1″. Combining circuitry S2 combines (e.g., adds) the signal Vm\with a higher frequency reference signal, VRF2, and outputs a signalthat is coupled to the second terminal 503 of the MEMS device C1″.Combining circuitry S3 combines (e.g., adds) the signal Vm2 with higherfrequency reference signal, VRF3, and outputs a signal that is coupledto the third terminal 505 of the MEMS device C1″. Combining circuitry S4combines (e.g., adds) the signal Vm2\ with a higher frequency referencesignal, VRF4, and outputs a signal that is coupled to the fourthterminal 506 of the MEMS device C1″. Measuring changes in capacitance inmovement and/or capacitance across the first terminal 502, the secondterminal 503, the third terminal 505, and/or the fourth terminal 506 andthe first common terminal 501, one or more modulated signals (e.g.,currents) indicative of the changes in movement/capacitance can begenerated. These modulated signals are coupled to amplifier circuitry504 via the first common terminal 501.

The output of amplifier circuitry 504 is coupled to bandpass filtercircuitry 516, 517, 518, 519. The bandpass filter circuitry 516, 517,518, and 519 pass signals related to the frequencies of the referencesignals, VRF1, VRF2, VRF3, and VRF4, respectively. The output, Vout516,of the bandpass filter circuitry 516 can be coupled to a firstdetection/demodulation circuitry (not shown) for the detection and/ordemodulation (e.g., in terms of amplitude or phase) of output signalVout516. The output, Vout517, of the bandpass filter circuitry 517 canbe coupled to a second detection/demodulation circuitry (not shown) forthe detection and/or demodulation (e.g., in terms of amplitude or phase)of output signal Vout517. The output, Vout518, of the bandpass filtercircuitry 518 can be coupled to a third detection/demodulation circuitry(not shown) for the detection and/or demodulation (e.g., in terms ofamplitude or phase) of output signal Vout518. The output, Vout519, ofthe bandpass filter circuitry 519 can be coupled to a fourthdetection/demodulation circuitry (not shown) for the detection and/ordemodulation (e.g., in terms of amplitude or phase) of output signalVout519.

In more-specific embodiments of the present disclosure, FIG. 5 depicts aMEMS mirror projector, including a MEMS device for scanning light into asurface. By evaluating each of the four sections (e.g., measuringindependently the movement/capacitance of the first terminal 502, thesecond terminal 503, the third terminal 505, and the fourth terminal 506across the first terminal 501 of the MEMS mirror), one or more errorcorrection signals can be combined with the signals Vm, Vm\, Vm2, andVm2\ at combining circuitry S1, S2, S3, and S4. Two or more of the errorcorrection signals may be similar or dissimilar. The one or more errorcorrection signals can be used to reduce and/or cancel cross-talkbetween the two scanning axes (e.g., the x-axis and the y-axis) of theMEMS device C1″ (e.g., the MEMS mirror projector), thus improving scanlinearity along the scanning axes.

The higher frequency (reference) signals VRF1, VRF2, VRF3, and VRF4 caninclude quadrature signals of the same or different frequencies. Forexample, VRF1 and VRF2 may be separated in phase by 90 degrees, but canthe same or different frequencies. Similarly, VRF2 and VRF3 can bequadrature signals separated in phase by 90 degrees, having the same ordifferent frequencies. As another example, VRF4 and VRF2 can bequadrature signals separated in phase by 90 degrees, having the same ordifferent frequencies. Since the high frequency reference signals VRF1,VRF2, VRF3, and VRF4 are quadrature signals having coupled to thembandpass filter circuitry 516, 517, 518, and 519 and synchronousdetectors 506 and 507 (as depicted in FIG. 4), recovery of signalinformation related to the higher frequency reference signals VRF1,VRF2, VRF3, and VRF4 is possible via modulation with the signals Vm,Vm\, Vm2, and Vm2\.

Bandpass filter circuitry 516-519 depicted in FIG. 5 can be configuredand arranged to pass the fundamental frequency and/or various otherharmonic frequencies related to the signals Vm or Vm2. For instance, ifthe frequency of Vm is fmod and the and the frequency of Vm2 isf_(mod2), then the harmonic frequencies of Vm include n×f_(mod) where nis an integer, and the harmonic frequencies of signal Vm2 includem×f_(mod2) where m is an integer. In various embodiments, aspects of thepresent disclosure are directed to determining static or time varyingharmonic distortion of the MEMS device C1″ by monitoring (e.g.,measuring) changes in movement and/or capacitance across at least one ofthe first terminal 502 and the first common terminal 501″, the secondterminal 503 and the first common terminal 501″, the third terminal 505and the first common terminal 501″, and/or the fourth terminal 506 andthe first common terminal 501″ of the MEMS device C1″.

Depicted in FIG. 6 is detection/demodulation circuitry and/or functionsfor modulating signals (e.g., in terms of amplitude and/or phase). InputIn_A of detection/demodulation circuitry 526, input In_B ofdetection/demodulation circuitry 527, input In_C ofdetection/demodulation circuitry 528, and input In_D ofdetection/demodulation circuitry 529 can be coupled to output filter(s)(not shown). The output signals, Vdet_A, Vdet_B, Vdet_C, and Vdet_D, ofdetection/demodulation circuitry 526, 527, 528, and 529 can be coupledto, for example, a spectrum analyzer to measure harmonic and/orintermodulation distortion of the signals. The output signals Vdet_A,Vdet_B, Vdet_C, and Vdet_D can be coupled to filter circuitry (notshown) for the purposes of measuring the time varying harmonic and/orintermodulation distortion related to one or more modulation signals(e.g., Vm, Vm\, Vm2, and/or Vm2\ of FIG. 5). Additionally and/oralternatively, the output signals Vdet_A, Vdet_B, Vdet_C, and Vdet_D canbe used to evaluate intermodulation distortion that is time varying orthat is static. For example, the output signals Vdet_A, Vdet_B, Vdet_C,and Vdet_D can be coupled to filter circuitry to assess theintermodulation distortion at one or more frequenciesp×f_(mod)±q×f_(mod2) wherein p and q are integers. For example a filterbank will pass a signal or signals of at least one frequency ofp×f_(mod)±q×f_(mod2). Phase or phase modulation of an intermodulationdistortion signal may be measured via a phase detector/demodulator witha reference phase signal derived from a frequency ofp×f_(mod)±q×f_(mod2).

The detection/demodulation circuitry 526, 527, 528, and 529 depicted inFIG. 6 can recover signals related to the movement and/or capacitance asmeasured across various portions of a MEMS device, for instance thefirst terminal 502 and the first common terminal 501 of the MEMS deviceC1″ of FIG. 5. The detection/demodulation circuitry 526, 527, 528, and529 can include circuitry for the modulation and/or demodulation ofsignals in terms of amplitude and/or phase. The output signals Vdet_A,Vdet_B, Vdet_C, and Vdet_D can be coupled to amplifier circuitry, theamplifier circuitry can include differential amplifier circuits. Forexample, supposing a MEMS device including two plates, two stators,and/or two rotors, the output signals Vdet_A and Vdet_B can be coupledto differential amplifier circuitry configured and arranged to perform asubtraction function (e.g., providing a difference signal ofVdet_A−Vdet_B) to generate a net signal for the supposed MEMS device.

The signals Vdet_A, Vdet_B, Vdet_C, and Vdet_D output by thedetection/demodulation circuitry 526, 527, 528, and 529 can undergo aFast Fourier Transform (FFT), be coupled to a spectrum analyzer, and/orbe coupled to filter circuitry 538 as depicted in FIG. 7. The filtercircuitry 538 can be configured and arranged to pass a fundamentaland/or harmonic frequency of a modulating signal (e.g., Vm, Vm\, Vm2,Vm2\ from FIG. 5). If, for example, the frequency of a first modulatingsignal is 900 Hz and the frequency of a second modulating signal is 3500Hz, the filter circuitry 538 can be configured and arranged as bandpassfilters having a fundamental frequency of 900 Hz (the frequency of thefirst modulating signal), a second harmonic at 1800 Hz (twice thefrequency of the first modulating signal), 3500 Hz (the frequency of thesecond modulating signal), and 10,500 Hz (the third harmonic of thesecond modulating signal). The filter circuitry 538 outputs signals o1,o2, o3 . . . oN, oN representing the Nth bandpass filter circuitincluded in the filter circuitry 538. Additionally and/or alternatively,oN can represent the Nth bandpass frequency of the filter circuitry 538.One or more signals output by the filter circuitry 538 can display, inreal-time and/or near real-time, measurements of the fundamental and/orharmonic frequencies of one or more signals indicative of the movementand/or capacitance of one or more mechanical, electro-mechanical, and/orcapacitive portions of a MEMS device (e.g., an electrostaticmicroactuator). The MEMS device can be a multi-dimensional device (e.g.,have at least an x-axis and a y-axis).

Signals output by the filter circuitry 538 can be coupled to circuitry539 for detecting the amplitude and/or phase of the fundamental and/orharmonic frequencies of these signals. When measuring the phase,reference to one or more input signals (e.g., the signals Vm and/or Vm2of FIG. 5, or signals related thereto) can be related to a first and/ora second axis of a MEMS device. The fundamental and/or harmonicfrequencies of the signals output by the filter circuitry 538.

Depicted in FIG. 8 is a multi-dimensional device, C1″, receiving asinputs carrier signals VI_1, VQ_1, VI_2, and VQ_2. The signals VI_1 andVQ_1 are in quadrature, as are the signals VI_2 and VQ_2 in quadrature.Also received as input signals are modulating signals Vm, Vm\, Vm2, andVm2\. The modulating signal Vm is combined with the carrier signal VI_1at combining circuitry 51, which outputs a signal that is coupled to afirst terminal 502 of the MEMS device C1″. The modulating signal Vm\ iscombined with the carrier signal VQ_1 at combining circuitry S2, whichoutputs a signal that is coupled to a second terminal 503 of the MEMSdevice C1″. The modulating signal Vm2 is combined with the carriersignal VI_2 at combining circuitry S3, which outputs a signal that iscoupled to a third terminal 505 of the MEMS device C1″. The modulatingsignal Vm2\ is combined with the carrier signal VQ_2 at combiningcircuitry S4, which outputs a signal that is coupled to a fourthterminal 506 of the MEMS device C1″. A first common terminal 501 of theMEMS device C1″ couples the signals output by the combining circuitryS1, S2, S3, and S4 to amplifier circuitry 504. The frequency of thefirst carrier signal, VI_1, and the second carrier signal, VQ_1, is thesame. The frequency of the third carrier signal, VI_2, and the fourthcarrier signal, VQ_2, is the same. The frequency of the first carriersignal, VI_1, and the second carrier signal, VQ_1, is different from thefrequency of the third carrier signal, VI_2, and the fourth carriersignal, VQ_2.

Amplifier circuitry 504 can output a signal that is input to a firstfiltering and detection circuitry 537, having a filter (e.g., a bandpassfilter) which passes signals related to the first and/or second carriersignal(s). The first filtering and detection circuitry 537 outputs asignal indicative of the capacitance across the first terminal 502 andthe first common terminal 501 and/or a signal indicative of thecapacitance across the second terminal 503 and the first common terminal501 of the MEMS device C1″. The first filtering and detection circuitry537 can include a first demodulation circuit (e.g., circuitry for thedetection/demodulation of a signal in terms of amplitude and/or phase)which outputs signals Vo502I and/or Vo503Q. The output signals Vo502Iand Vo503Q are indicative of the movement and/or capacitance measuredacross the first terminal 502 and the first common element 501 and themovement and/or capacitance measured across the second terminal 503 andthe first common terminal 501 of the MEMS device C1″, respectively.Filtering and detection circuitry 537 can receive one or more referenceinput signals (e.g., Vref1′I and/or Vref1′Q) for providing synchronousdetection and/or demodulation of a modulated signal received at thefirst terminal 502 and/or the second terminal 503 of the MEMS deviceC1″.

Additionally and/or alternatively, amplifier circuitry 504 can output asignal that is input to a second filtering and detection circuitry 536,having a filter (e.g., a bandpass filter) which passes signals relatedto the third and/or fourth carrier signal(s). The second filtering anddetection circuitry 536 outputs a signal indicative of the capacitanceacross the third terminal 505 and the first common terminal 501 and/or asignal indicative of the capacitance across the fourth terminal 506 andthe first common terminal 501 of the MEMS device C1″. The secondfiltering and detection circuitry 536 can include a second demodulationcircuit (e.g., circuitry for the detection/demodulation of a signal interms of amplitude and/or phase) which outputs signals Vo505I and/orVo506Q. The output signals Vo505I and Vo506Q are indicative of themovement and/or capacitance measured across the third terminal 505 andthe first common element 501 and the movement and/or capacitancemeasured across the fourth Filtering and detection circuitry 537 canreceive one or more reference input signals (e.g., Vref1′I and/orVref1′Q) for providing synchronous detection and/or demodulation of amodulated signal received at the first terminal 502 and/or the secondterminal 503 of the MEMS device C1″. Filtering and detection circuitry536 can receive one or more reference input signals (e.g., Vref2′Iand/or Vref2′Q) for providing synchronous detection and/or demodulationof a modulated signal received at the third terminal 505 and/or thefourth terminal 506 of the MEMS device C1″.

The signals Vo502I and Vo503Q can be input to a first differentialamplifier circuit, which outputs a signal indicative of the combinedcapacitance, movement, and/or position of the first terminal 502 and thesecond terminal 503 relative to (e.g., across) the first common terminal501 of the MEMS device C1″. The signals Vo505I and Vo506Q can be inputto a second differential amplifier circuity, which outputs a signalindicative of the combined capacitance, movement, and/or position of thethird terminal 505 and the fourth terminal 506 relative to (e.g.,across) the first common terminal 501 of the MEMS device C1″.

Circuitry 538 can be configured and arranged to perform spectrumanalysis, Fast Fourier Transform (FFT), and/or additional filteringoperations on the signals output by the filtering and detectioncircuitry 536 and 537. The circuitry 538 can provide real-time and/ornear real-time measurements of fundamental frequency signals, harmonicdistortion signals, and/or intermodulation distortion signals. Signalsoutput from the circuitry 538 are, for example, o1, o2, o3, o4, o5, o6,o7, o8, o9, and or oN, wherein oN denotes an Nth output signal from thecircuitry 538. In specific embodiments, a combination of signals of thefirst terminal 502 and the second terminal 503 is provided when forexample the phase angle of Vref1′I→45 degrees instead of 0 degrees(wherein the original phase angle of Vref1′I was 0 degrees), and anoutput signal is provided from Vo502I or Vo503Q. Other phase angles maybe used for Vrref1′I. In another embodiment a combination signal ofelements 505 and 505 is provided when the phase angle of Vref2′1→45degrees instead of 0 degrees (wherein the original phase angle ofVref1′I was 0 degrees), and an output signal is provided via Vo505I orVo506Q. Other phase angles may be used for Vref2′I. Output signals fromthe first and/or second filtering and detection circuitry 537 and or 536may be coupled to circuitry 538 a spectrum analyzer, FFT (Fast FourierTransform), and/or additional filtering circuitry. The additionalfiltering circuitry included in the circuitry 538 provides instantaneousmeasurement of fundament frequency signals, harmonic distortionsignal(s), and or intermodulation distortion signal(s).

FIG. 9 illustrates exemplary filtering circuitry that can be included inthe additional circuitry 538 of FIG. 8. Input line 104′ can be used toinput the signals output by detection/demodulation circuitry (e.g. theoutput signals Vdet_A, Vdet_B, Vdet_C, and Vdet_D ofdetection/demodulation circuitry 526, 527, 528, and 529, respectively ofFIG. 6) to filters 105, 106, and 107. While only three additionalfiltering circuitry are shown, it should be understood that as many as Nfilters can be included in the additional filtering circuitry, where Nis the same integer used to denote an Nth output signal from thecircuitry 538 as seen in FIG. 8. Filtering circuitry included in thefilters 105, 106, and 107 can include bandpass filter circuitry, and/orother types of circuitry permitting the passage of the fundamentalfrequency and/or the harmonic frequencies of any modulation or drivesignals received as inputs to a MEMS device (e.g., the multi-dimensionalMEMS device C1″ of FIG. 8), upstream of the filters 105, 106, and 107.

The filters 105, 106, and 107 can pass signal(s) includingintermodulation distortion signals, or signals that can be described byan intermodulation signal having a frequency=n×f_(mod) _(_) ₁±m×f_(mod)_(_) ₂, where n and m are integers, f_(mod) _(_) ₁ is a drive ormodulation frequency of a first axis, and f_(mod) _(_) ₂ is a drive ormodulation frequency of a second axis of a multi-dimensional MEMSdevice. Furthermore, intermodulation distortion signals have frequenciesrelated to two or more drive signals, the two or more drive signalshaving different frequencies from one another. Additionally and/oralternatively, the intermodulation distortion signals can havefrequencies and/or phases related to two or more drive signals, thedrive signals having similar and/or the same frequencies. In instanceswhen the two (or more) drive signals have the same frequency, theintermodulation signals provide distortion signals which are related tothe phase/phase angles of the two or more drive signals. Differences inthe phase angles generally provide a show rate change in amplitude ofthe intermodulation distortion signal when the frequencies causing thedistortion are the same (e.g., cos [α(t)−β(t)] where α(t) and or β(t)are phase angles of one or more drive or modulating signals, and orwhere α(t) and or β(t) may include time dependent (or time independent)phase angle values).

The output signal(s) of filters 105, 106, and 107 can be coupled tocircuitry for measuring the amplitude of a signal (e.g., an amplitudedetector) and/or circuitry for measuring the phase of a signal (e.g., aphase detector). Such amplitude and/or phase detection circuitry can beused for measuring amplitude/phase modulation, amplitude/phasedifferences between reference signals (e.g., reference a drive ormodulating signal related to a harmonic of an input drive or modulatingsignal). Amplitude detection circuitry 108, 109, 110 can receive asinputs a signal(s) relating to the fundamental and/or harmonicfrequencies of a drive and/or modulating signal output by the filtercircuitry 105, 106, 107. For example, filter 105 can pass signal(s)related to the fundamental frequency of a drive signal, filter 106 canpass signal(s) related to the second harmonic of the drive signal, andfilter 107 can pass signal(s) related to the Nth harmonic of the drivesignal. Information related to amplitude and/or related to thefundamental frequency and/or harmonic frequencies of these signals canbe output as signals Vout1AM, Vout2AM, and Vout3AM. Additionally and/oralternatively, phase detection circuitry 111, 112, 113 can receive asinputs the signal(s) output by filters 105, 106, and 107 along withsignal(s) VLF, VLF′, and VLF″, respectively. The signals VLF, VLF′, andVLF″ are reference signals to the detection circuitry 111, 112, and 113.The reference signal VLF can be a signal related to a drive signal atthe fundamental frequency, the reference signal VLF′ can be a signalrelated to a harmonic frequency (e.g., the second harmonic) of a drivefrequency, and the reference signal VLF″ can be related to a higherharmonic (e.g., the Nth harmonic) of a drive signal. The signals VLF,VLF′, and VLF″ can be derived from one or more (input) drive signals.Information related to the modulation and/or the phase of a drive signalcan be provided by Vout1PD, Vout2PD, and/or Vout3PD.

Various embodiments of the present disclosure are directed todetection/demodulation circuitry 108-113 including circuitry fordemodulating signals (e.g., in terms of amplitude and/or phase). Forexample, a MEMS device connected to an oscillator circuit (not shown)for providing frequency modulation generally has a frequencydemodulation circuit coupled to the oscillator circuit. The output ofsuch a frequency demodulation circuit can be, for example, coupled tothe input line 104′ as depicted in FIG. 9.

In additional embodiments, the phase difference between the signalsVout1 and Vout2, as depicted in FIG. 9, can be measured by recordingdifferences in the fundamental and/or harmonic frequencies of thesignals Vout1 and Vout2, once they have passed through the filters 105and 106, respectively. Additionally and/or alternatively, the signal VLFcan be coupled to Vout2 that includes a harmonic frequency signal, whichthen has one input of detection/demodulation circuitry 111 coupled toVout1 and the other input of detection/demodulation circuitry 111coupled to Vout2. The output of detection/demodulation circuitry 111,Vout1PD, is indicative of the phase or phase modulation between afundamental frequency signal and a harmonic frequency signal (e.g.,harmonic distortion signal). Detection/demodulation circuitry 112 canmeasure phase or phase modulation between two signals of differentharmonic distortion (e.g., an Nth harmonic and an Mth harmonic where Nis not equal M). For example, VLF′ may be coupled to Vout3 such that oneinput of detection/demodulation circuitry 112 is couple to Vout2 whilethe input of detection/demodulation circuitry 112 is coupled Vout3 toprovide an output signal Vout2PD of detection/demodulation circuitry 112that provides a signal indicative of phase or phase modulation betweentwo harmonic distortion signals. The two harmonic distortion signals caninclude harmonic distortion signals from a multi-dimensional MEMS devicesuch as a signal indicative of x-axis harmonic distortion, and a signalindicative of y-axis harmonic distortion. The multi-dimensional MEMSdevice can further include an Nth harmonic distortion signal for the x-xis and an Mth harmonic distortion signal for the y-axis, where N and Mare integers. Detection/demodulation circuitry 108-113 can coupled tothe output of a filter (e.g. 105, 106, and/or 107) for measuring thefundamental and/or harmonic frequency from a first axis (e.g., thex-axis) of a multi-dimensional MEMS device, with a phase of afundamental and/or harmonic frequency related to the second axis (e.g.,y-axis) of the multi-dimensional MEMS device.

FIG. 10 depicts a multi-dimensional MEMS device C1 configured andarranged in part of a feedback system/loop, in accordance with aspectsof the present disclosure. A drive signal, Vd, is input to combiningcircuitry (e.g., an adder) S3 along with a signal Vpr. The signalresulting from the combination of the drive signal Vd and the signal Vprat combining circuitry S3 is input to drive amplifiers A1 and A2. Thesignal Vpr can include an error signal. The drive amplifiers A1 and A2output push/pull, differential, and/or complementary signals to thecombining circuitry S1 and S2, respectively. The combining circuitry S1combines (e.g., adds) a high frequency carrier signal V1 with the signaloutput by driver amplifier A1 at the first terminal 502 of MEMS deviceC1. The combining circuitry S2 combines (e.g., adds) a high frequencycarrier signal V2 with the signal output by driver amplifier A2 at thesecond terminal 503 of the MEMS device C1. The high frequency carriersignals V1 and V2 can include quadrature signal(s) and/or signalcomponents which are +/−90 degrees out of phase. Additionally and/oralternatively, the high frequency carrier signals V1 and V2 can includethe same signal(s) and/or (quadrature) signal components.

A first common terminal 501 of the MEMS device C1 can provide a signalas an input to amplifier circuitry 504 which is indicative of themovement and/or capacitance across the first terminal 502 and the firstcommon terminal 501 and/or across the second terminal 503 and the firstcommon terminal 501 of the MEMS device C1. The signal(s) output byamplifier circuitry 504 is input to circuitry 516 for filtering (e.g.,providing a bandpass filter function) said signal before outputtingsignal Vout516 which, in turn, is input to detection/demodulationcircuitry 536. The signal Vout516 is a modulated signal (e.g., modulatedin terms of amplitude and/or phase). The detection/demodulationcircuitry 536 can include circuitry for detecting amplitude modulationof quadrature signals, circuitry for detecting phase modulation ofquadrature signals, and/or an envelope detector. Output signal Vdet1Afrom detection/demodulation circuitry 536 is input to processorcircuit/function 537 which can include a means of amplifying an inputsignal (e.g., Vdet1A) before outputting a signal (e.g., Vpr) therefrom.

Depicted in FIG. 11 is circuitry for the detection/demodulation (e.g.,in terms of amplitude and/or phase) of quadrature signals. An amplitudemodulation signal, AM Sig is defined as an “I signal” (I sig), that iscoupled to an input (e.g., In3) of squaring function, block 604. Anothersignal, AM Sig, is also coupled to a phase shifter (e.g., via In1),block 602, which provides a 90 degree phase shift to signals around thecarrier frequency of the amplitude modulation signal, AM Sig. An outputsignal, OutP of the phase shifter 602 provides an amplitude modulatedsignal that includes a quadrature phase carrier signal. For example, theoutput of the phase shifter transforms AM Sig to a new amplitudemodulation signal wherein the carrier signal has been shifted in phaseby 90 degrees, which provides a Q signal, Q sig. The phase shiftedcarrier amplitude modulation signal, Q sig, is coupled to a squaringfunction/circuitry 603, the output of which is a squared, modulated,quadrature carrier signal OutQ_SQ, which can be described as (Q sig)².The output of squaring function/circuitry 604 provides a squared,in-phase carrier signal OutI_SQ, which can be described as (I sig)².Summing function/circuitry 605 combines/sums OutQ_SQ with OutI_SQ toprovide a signal at Out5=(I sig)²+(Q sig)². For a small modulation indexwherein the carrier amplitude changes by a small amount (e.g., <10% or<10% modulation on a carrier signal), the signal from Out5 or Vo5, whichis the sum of the squares of I sig and Q sig, or [(I sig)²+(Qsig)²]=Vo5, will provide an AM demodulation signal with sufficiently low(e.g., demodulation) distortion. In some examples, the depth ofmodulation or modulation index is sufficiently low and the sum of thesquares of I sig and Q sig will provide AM demodulation for DetectorDET_A block 536 in FIG. 11 (e.g., a feedback system for linearizingposition or scanning in a MEMS device). To ensure low distortiondemodulation for any amount of modulation index (e.g., including up to100% modulation), OutS is coupled to an input of a square root functionor circuit, block 606. An output signal, Vo6, from the square rootfunction/circuit 606 then provides demodulation of an amplitudemodulation signal. Output signal Vo6 can be characterized as:

Vo6√{square root over ((I sig)(I sig)+(Q sig)(Q sig))}

Note in either demodulation signals Vo5 or Vo6, there is no low passfilter required to remove carrier signals because the carrier signalsare cancelled via summer/combiner 605 in FIG. 11. The lack of requiringa low pass filter provides an advantage in that the IQ demodulator inFIG. 11 provides minimal phase shift during the demodulation process torecover the modulated signal. Note that the phase shifter 602 isproviding a phase shift at the higher carrier frequency. For example, atypical carrier frequency may be in the 1 MHz range, while the (e.g.,recovered) modulated signal may have a frequency range from 100 Hz to 10kHz. Low pass filtering (e.g., using a conventional AM detector such asan envelope detector with a hold capacitor and low pass filter) for a 10kHz bandwidth provides more phase shift than a phase shifter circuitoperating at 1 MHz.

FIG. 12 shows examples of detectors, demodulators, and or filters. Asynchronous detector or synchronous demodulator is shown via 635, amultiple input multiplier with input terminals In1 and In2. The outputof the synchronous detector or multiplier supplies a signal, OutSD1. Forexample, if a first signal Vin1 st is coupled to Inl and a second inputsignal, Vin2 nd is coupled to In2, the output is characterized ordescribed as OutSD1=k×Vin1 st×Vin2 nd, where k is a constant. A phasedetector (e.g., that includes 636, Lim1, and or Lim2) wherein zerocrossing of input signals are utilized to measure phase is shown withlimiter functions or circuits, Lim1 and Lim2. Input terminals ILim1 andILim2 are coupled to input signals, wherein a first input signal may bea reference phase signal to be compared with a second input signal forphase measurement. The limiter functions or signals may include acomparator circuit or a mathematical equivalent or similar to a sgnfunction (e.g., sgn(x)=−1 if x<0, sgn(x)=+1 if x>0). Output signals fromthe limiters, OLim1 and OLim2 are coupled to inputs of a synchronousdetector or to a multiplier, 636. An output signal OutPD1 of 636provides a phase detector signal, which can be coupled to a low passfilter (e.g., such as a resistor capacitor low pass filter) to remove(e.g., higher frequency) signals related to OLim1 and OLim2; the lowpass filter generally has lower frequency signals than those from Lim1and or Lim2; the low pass filter coupled to OutPD1 provides a signalindicative to a phase difference between the two input signals to ILim1and ILim2.

In certain implementations, a phase detector circuit includes anexclusive or XOR gate such as a two input XOR gate, and/or a flip flopcircuit of function. Block 637 shows an example Set−Reset Flip Flop(e.g., also known as an RS flip flop) included for a phase detector. Afirst input signal is coupled a Set input terminal, InS, and a secondinput signal is coupled to a Reset input terminal, InR. Generally theinput terminals of flip flop 637 are edge trigged or can be leveltriggered. Output signal Qo of a Set Reset flip flop goes high when apulse is transitioned to logic high at the S (set) input, and Qo goeslow when a pulse is transitioned from a logic high at the R (reset)input. Flip flop 637 provides an output signal Qo that provides a pulseincluding a duration dependent on a time (or phase) difference betweenthe two input signals (e.g., first and second input signals). The outputsignal Qo is coupled to an input terminal, InF, of a Filter (e.g., 638).The output signal, O_F, of Filter 638 removes or attenuates signalsrelated to the input terminals at InS and or InR. An example peakdetector or envelope detector for demodulating an AM signal (amplitudemodulated signal) is shown via D1, C2, R2, R3 and C3. An AM signal iscoupled to input terminal Vin_d, a first terminal of a diode, D1. Asecond terminal of the diode, D1, is coupled to a peak hold capacitor C2and to a resistor R2 to discharge capacitor C2. A signal, Vo_fil,provides a demodulated AM signal with a recovered modulated signal(e.g., lower frequency signals compared to the higher carrier frequencysignal of an AM signal). The signal Vo_fil includes the recoveredmodulation signal and also some signals related to the carrier signal ofthe amplitude modulation signal. A low pass filter provided by R3 and C3removes or attenuates the carrier signal while passing through therecovered modulated signal. A band pass filter example is provided byR1, L1, and C1. Input to this band pass filter example is provided viaVin_f coupled to a first terminal of R1. A second terminal of R1 iscoupled to a first terminal of capacitor C1 and to a first terminal ofinductor L1. In this example, the second terminals of C1 and L1 aregrounded. The output of the band pass filter is provided via Vo_fil. Thebandwidth of the band pass filter example can be set or varied viavalues for R1, C1, and or L1. In some implementations, output signalVo_fil is coupled to an input terminal of an amplifier (e.g., bufferamplifier) to avoid loading on the output signal at Vo_fil. An examplehigh pass filter can be implemented by removing C1, leaving R1 and L1 toprovide a high pass filter. A low pass filter may be implemented viaremoving L1, leaving R1 and C1 as part of this low pass filter.

In one or more embodiments, one or more DC bias voltage(s) may becoupled to one or more elements of a microactuator, MEMS, orelectrostatic device as characterized herein.

In another embodiment including a multi-dimensional device (e.g., MEMSdevice), the resonant frequency of one axis (e.g., X axis) is varied bysupplying to another axis (e.g., Y axis) electrode an AC signal of anamplitude and or of a frequency. In one embodiment, the resonantfrequency of a first axis is controlled by varying an amplitude level ofan AC signal to a second axis. Another embodiment is directed tocontrolling the resonant frequency of a first axis by varying afrequency of an AC signal to a second axis. A DC voltage may be furthercombined with the AC signal of the second axis to provide furthercontrol of the resonant frequency of the first axis. For example, the ACvoltage to the electrode of the second axis can be increased in one ormore applications for lowering of the resonant frequency of the firstaxis. A variable frequency controlled resonator may be implemented usinga two (or more) dimensional device (e.g., MEMS or the like) that utilizean X axis electrode (e.g., an X axis resonator) for the resonator and aY axis electrode for controlling the resonant frequency and or bandwidth(e.g., Q of a resonator) of the X axis resonator. This control may beeffected via an AC signal with a particular frequency and or amplitudelevel supplied to the Y axis. An AC signal may include any combinationof: a sine wave, a continuous waveform, a modulated waveform (includingamplitude modulation, phase modulation, and or frequency modulation),and or an arbitrary waveform. In a particular embodiment, an AC waveformis supplied to a first axis of a multi-dimensional device to provide achange in effective mass in a second axis of a multi-dimensional device.The effective mass of the second axis is controllable via the amplitude,frequency, and or phase of the AC waveform.

Referring back to FIG. 5, an embodiment may be implemented as follows. Amulti-dimensional device, C1″, may include elements 502, 503, 505, 506,and 501″. Other circuitry such as amplifier 504, Rf, S1, S2, S3, S4,BPF1, BPF2, BPF3, and or BPF4 may be omitted, when controlling afrequency response of one of the axis of C1″. In one embodiment, atleast two elements of C1″ may be utilized for providing a resonantdevice that is dependent on an AC signal. A driving signal, Vm2 thatincludes an AC signal is coupled to one of the elements such as 505,which provides a change in frequency response in terms of the elements502 and or 503, where element 502 and or 503 can be used as a resonantdevice. For example, a tunable resonant device can be provided byelements 502, 503, and or 501″. Tuning for example, is provided by acontrol signal supplied to element 505 and or 506. The control signalincludes an AC signal and or a DC signal. The control signal includes anAC signal with or without a DC bias signal. In an example, the tunabledevice or frequency dependent device may include elements 502 and 501″,or 502 and 503, or 503 and 501″, or 502, 503, and 501″. Controlling theresonant frequency of C1″ or changing the frequency response of C1″(e.g., with elements 502 and 501″, or 502 and 503, or 503 and 501″, or502, 503, and 501″) is provided by coupling a signal to 505 and or 506.Note that although C1″ shows a common terminal or element (e.g., 501″) amulti-dimensional device may include one or more common terminals orelements.

In one or more embodiments the resonant frequency or frequency responseof a device may be changed via an AC signal, and at least onecharacteristic of the device may be changed in terms of: a phaseresponse, a frequency response, a sub resonant frequency response, adistortion characteristic including harmonic distortion and orintermodulation distortion. For example, by supplying an AC signal onone axis of the device, can provide a change in distortioncharacteristic(s) for the other axis of the device.

One or more embodiments may include a portion of the circuits or systemsillustrated in the figures. In at least one of the examples such in FIG.5, the device C1″ can be driven with a push pull signal (e.g., Vm andVm\). In some applications, MEMS or electrostatic devices may be drivenusing a single-ended approach. One or more embodiments may be applicableto single ended device. For example, in FIG. 5, elements 506 and or 503may be removed from device C1″, which for example will not require Vm1\,VRF4, VRF2, S2 and or S4; in this example elements 502 and or 505 may bedriven single ended by Vm and or Vm2.

In one or more embodiments the common element or common electrode (e.g.,501, 501′, and or 501″) is coupled to an input of an amplifier thatprovides a virtual AC ground. This virtual AC ground de-sensitizes straycapacitance from wiring or cables.

One or more embodiments may include a feedback system including amicroactuator and a quadrature detector comprising: a first higherfrequency signal source and a first drive signal source with themicroactuator including a first driven terminal and a first commonterminal. The first common terminal may be coupled to an input of anamplifier, an output signal may be coupled from the amplifier to aninput terminal of a first filter, and an output signal from the firstfilter may be coupled to an input terminal of the quadrature detector.The output signal from the quadrature detector, first drive signal, andthe first higher frequency signal source is coupled to the first driventerminal of the microactuator to provide a feedback system for themicroactuator.

Another example embodiment is directed to a system to vary a resonantfrequency of a multi-dimension microactuator device. The system includesa multi-dimension microactuator device having a first axis element and asecond axis element, as well as a first input terminal for the firstaxis element and a second input terminal for the second axis element. Afirst control signal is coupled to the first input terminal. The firstcontrol signal includes an alternating current signal and is supplied tothe first input terminal to change or vary a resonant frequency of thesecond axis element of the multi-dimension microactuator device. Anotherembodiment may include adding a direct current signal to the firstcontrol signal.

In accordance with one or more embodiments, an apparatus and/or methodare directed to monitoring the position of an electrostatically drivenresonator. Such aspects are directed to and/or may utilize resonantmicro-electro-mechanical systems-based (MEMS-based) devices and, inparticular applications, to systems for measuring the instantaneousposition of an electrostatically driven resonant MEMS-based device.Accordingly, methods and/or apparatuses of the disclosure may relate toevaluating or measuring the position of an electrostatic microactuator(e.g., MEMS device) in terms of phase and or amplitude characteristics.In certain embodiments, distortion characteristics of an electrostaticmicroactuator are characterized, measured or otherwise utilized toprovide increased detail as to how the microactuator is behaving.

Various embodiments are directed to a measurement system that mitigatesparasitic capacitance effects referenced to ground, or mitigating thedesensitizing of capacitance measurements due to the input capacitanceof lock-in amplifiers, such as those mentioned in Jingyan Dong andPlacid M. Ferreira, “Simultaneous actuation and displacement sensing forelectrostatic drives” 2008 TOP Publishing Ltd. (24 Jan. 2008). Certainembodiments are directed to a capacitance measurement system for MEMSdevices that facilitate FM measurement, such as by overcoming drift oroffset problems due to inductance and capacitance values changing withtemperature, such as may be implemented in connection with one or moreaspects of Steven L. Moore and S. O. Reza Moheimani, “SimultaneousActuation and Sensing for Electrostatic Drives in MEMS using FrequencyModulated Capacitive Sensing,” IFAC Proceedings Vol. 47, Issue 3, 2014,pp 6545-=6549 (e.g., with FIG. 3 therein).

Certain embodiments are directed to providing a measurement system thatcharacterizes nonlinearities of the MEMS device while be driven intodistortion, or driven into gross distortion that is not characterizedaccurately by a third order differential equation model such as aDuffing equation. A Duffing or nonlinear equation may be expressed as:

{umlaut over (x)}+δ{dot over (x)}+kx±βx ³=γ cos(ωt)

Further embodiments are directed to measuring a MEMS device or systemwherein equations that approximates nonlinear behavior, mitigatingdistortions due to overdriving the MEMS device, addressing such issueswith an equation as:

{umlaut over (x)}+δ{dot over (x)}+kx±βx ³=γ cos|(ωt)

which may be challenging to predict due to the use of polynomials formodeling the nonlinear behavior of the MEMS device.

Other embodiments are directed to measuring multiple modes of a MEMSdevice (or a microactuator) wherein two or more different resonantfrequencies are identified and characterized in terms of distortion,amplitude, and or phase characteristics. Certain embodiments involvecharacterizing the nonlinearity of a MEMS (or microactuator) device byusing a plurality of filter circuits, amplitude detectors, and or phasedetectors to measure the amplitude and phase responses at thefundamental frequency and or measure the amplitude and phase responsesat one or more harmonic frequencies. Still other embodiments involvemeasuring the displacement or deflection of a microactuator (or MEMSdevice) for an amplitude modulation effect and or a phase modulationeffect. The amplitude modulation effect and or phase modulation effectmay be measured at a fundamental frequency and or a harmonic frequencyof one or more of the following: a dominant mode or normal modefrequency, a sub-mode frequency, and or a spurious mode frequency.

In some embodiments, a measurement system shows dynamic changes (e.g.,modulation) or nonlinear effects (e.g., distortion) over the frequencyband of the MEMS device. The measurement system includes spectrumanalysis of the MEMS capacitance signal when the MEMS device is drivenat a frequency near or at its resonant frequency and or when the MEMSdevice is driven at a mode frequency that is not equal to the dominantresonant frequency. This MEMS capacitance signal may include a distortedwaveform such as a parabolic waveform that is indicative of the MEMScapacitance when driven by a sinusoidal waveform. In some experiments,it has been found for example, that a microactuator or MEMS device whencoupled to a sinusoidal signal of a fundamental frequency resulted in adistorted or non-sinusoidal displacement or motion. This distorteddisplacement or motion when decomposed by spectral analysis showedsinusoidal signals at the fundamental frequency and at harmonics of thefundamental frequency, wherein some experiments the amplitude of theharmonic signal was equal or greater than the signal at the fundamentalfrequency.

FIG. 4A shows an embodiment that includes a first detector, 104, todemodulate the modulated high frequency signal and provide a signal,Vout104 that is indicative of capacitance changes of the MEMS device102, or C1. In FIG. 4A there are shown three input signals, VDC, a DC(direct current) voltage biasing signal to the MEMS device, VLF, a lowfrequency driving signal that results in displacement or deflection ofthe MEMS device, and VHF a signal that provides a high frequency signalthat is not responsive from the MEMS in terms of displacement ordeflection. Note that the DC bias voltage, VDC, coupled to themicroactuator or MEMS device may be included or not included. Also, VDCmay include a zero voltage or some other DC voltage. Signals VLF, VHF,and VDC provide a low impedance/resistance voltage drive to a firstterminal of the MEMS device, C1. This low impedance/resistance voltagedrive is essentially not affected by frequency/phase response by thecapacitances of the MEMS capacitance, C1, and its parasitic capacitance,Cpar1. By having voltage driven signal into the MEMS device, the changesin MEMS capacitance are accurately reproduced at the output of thetrans-resistance amplifier 103. Note that trans-resistance amplifier maybe substituted with a common base or common gate amplifier that bothhave low input resistances. Signal VHF via signal VLF will provide anamplitude modulated capacitor current, I_C_MEMS flowing into atrans-resistance amplifier, 103. The input resistance (e.g., Rin) intothe trans-resistance amplifier 103 is a low resistance/impedancecompared to the impedance of parasitic capacitance, Cpar2; this resultsin that Cpar2 have no effect on measuring the capacitor current from theMEMS device because virtually all the MEMS capacitor current flows intothe trans-resistance amplifier 103. Put in another way, the voltage at(−) input terminal of amplifier 103 is a virtual short circuit to groundvia negative feedback resistor Rf. Therefore, with no voltage acrossCpar2, there is no AC current flowing into Cpar2. The output signal fromamplifier 103 is coupled to a filter (e.g., a filter or band pass filterwithin block 104) to remove the signal related to VLF while passing asignal related to VHF. For example, filter-amplifier-detector block 104may include a high pass filter and or a bandpass filter, an amplifier,and or an AM (amplitude modulation) detector. After the AM detector,Block 104 may also include a low pass filter or band reject filter toremove signal(s) related to VHF. When driving the MEMS devices outsideof its linear displacement region, the system shown in FIG. 4A allowsfor analysis of the signal from 104, which generally includes adistorted waveform to be analyzed in detail. For example, the outputsignal Vout104 may be coupled to a spectrum analyzer, FFT (Fast FourierTransform), or other spectrum and or phase analysis system.

The output signal Vout104 may be coupled to another amplitude modulationdetector to provide a signal indicative of the amplitude of Vout104 as afunction of time that may include showing amplitude modulation effect(s)of Vout104, wherein Vout104 may include a distorted waveform.

In FIG. 4A as an example, the output signal Vout104 is coupled to atleast one filter such as Filter 1 that may pass signals related to thefrequency of the input signal VLF. Filter 1 may include a low passfilter, high pass filter, and or band pass filter. The output of Filter1 provides an output signal Vout1, which is coupled to amplitudedetector/demodulator, DET1A and or to a first input terminal of phasedetector/demodulator DET1P. A second input terminal DET1P is coupled tothe input signal VLF. An output signal Vout1AM from DET1A provides asignal indicative of amplitude level which may include time varyingamplitude a recovered signal of the (e.g., fundamental) frequency of theinput signal VLF. An output signal Vout1PD from DET1P provides a signalindicative of phase modulation or static phase from Fitler1 thatpertains to the fundamental frequency of VLF in relationship from theinput signal VLF. To provide further detail on the MEMS displacementcharacteristics, another filter, Filter2 is utilized to pass a signalwhose frequency is other than the frequency of signal source VLF. Forexample, Filter2 may pass the second harmonic signal or a signal that istwice the frequency of VLF. Filter2 may include a band-pass filter, highpass filter, and or low pass filter. The output signal Vout2 fromFilter2 is coupled to an amplitude detector DET2A and or to a firstinput terminal phase detector DET1P. A second input terminal of phasedetector DET2P is coupled to a signal related to the input signal VLF.For example, as shown in FIG. 4A VLF′ that is coupled to the secondinput terminal of DET2P can be a twice frequency signal or secondharmonic of VLF. In one example, a signal generator with a commonfrequency clock can generator in synchronous multiple output signalwherein a fundamental frequency and at least one harmonic frequency thatare synchronized. The output signal Vout2AM for example providesmeasurement of static or time varying amplitude level of the secondharmonic component from Vout104. Similarly Filter3 can pass an Nthharmonic signal from Vout104 that allows for analyzing the Nth harmonicfrom Vout104 in terms of static or time varying amplitude and or foranalyzing the Nth harmonic from Vout104 in terms of static or timevarying phase. Vout3 from the output of Filter 3 is coupled to amplitudedetector DET3A and or to a first input terminal of phase detector DET3P.A second input terminal of DET3P is coupled to VLF″ wherein VLF″ is asignal related to VLF. For example, VLF″ may include an Nth harmonicsignal of VLF.

As an illustrative example for the apparatus in FIG. 4A, a MEMS devicewith driven with a DC bias voltage, VDC=40 volts DC, and with a lowfrequency signal

VLF=15 sin[(2π90 Hz)t], and VHF=sin[(2π 1000 kHz)t], or put in anotherway, VLF is a 900 Hz sine wave with 15 volts peak and VHF is a 1000 kHzsine wave at 1 volt peak. Note that other frequencies and or amplitudesfor signals VLF and or VHF may be used. Also different DC bias voltagesfor VDC may be used. The VLF signal modulates the capacitance of C1 at900 Hz sine wave and provides an amplitude modulated 1000 kHz signal viathe capacitor current of C1. This amplitude modulated 1000 kHz isgenerally at least a slightly distorted modulated waveform because theMEMS device is not displacing linearly, which results in non-linear ordistorted capacitor current, I_ C_MEMS. The output of preamp 103,Vout_preamp, provides a modulated 1000 kHz signal with one or moremodulation frequencies related to VLF or 900 Hz (e.g., 900 Hz, 1800 Hz,2700 Hz, or N×900 Hz, where N is an integer). The Voutpreamp signal iscoupled to a band pass filter in block 104 to pass signals around thefrequency of VHF (e.g., pass signals around 1000 kHz). For example, thefilter in block 104 may include a band pass filter that passes signalsfrom 980 kHz to 1020 kHz that result in a bandwidth of 40 kHz, and arecovered demodulated bandwidth following the Det 104 is half of 40 kHz,which is 20 kHz. The output signal of the detector, Det 104, Vout104 isthen coupled to one or more band pass filter(s) at the fundamentalfrequency (e.g., 900 Hz) of VLF and or a harmonic of the frequency ofVLF (e.g., harmonic includes N×900 Hz such as 1800 Hz or 2700 Hz). Forexample, Filter 1 or block 105 may include a band pass filter for 900Hz, Filter 2 or block 105 may include a band pass filter for 1800 Hz,and or Filter 3 may include a band pass filter for 2700 Hz (or anotherfrequency). The bandwidth range of Filter 1, Filter 2, and or Filter 3may be in the range of 1 Hz to at least 100 Hz, however a differentbandwidth range or frequency range can be chosen for any of the filtersin block(s) 105, 106, and or 107. The output of block 104 is coupled tothe input(s) of filter blocks 105, 106, and or 107. The output ofFilter1 is coupled to an input of an amplitude detector DET1A (block108), and to the output of DET1A provides an output signal VoutlAM thatprovides a signal indicative of the strength of amplitude (e.g., in thetime domain) of the fundamental frequency of VLF via the MEMSdisplacement characteristic. The output of Filter2 is coupled to aninput of an amplitude detector DET2A (block 109), and the output ofDET2A provides an output signal Vout2AM that provides a signalindicative of the strength of amplitude (e.g., in the time domain) ofthe second harmonic frequency of VLF via the MEMS displacementcharacteristic. Filter3 block 107 may be optional. The output of Filter3is coupled to an input of an amplitude detector DET3A (block 110), andthe output of DET3A provides an output signal Vout3AM that provides asignal indicative of the strength of amplitude (e.g., in the timedomain) of the third harmonic frequency of VLF via the MEMS displacementcharacteristic.

In an example to measure static phase and or time varying phasecharacteristic of the MEMS device, the output of Filter1 is coupled to afirst input terminal of phase detector, DET1P (e.g., block 111) and asecond input terminal of phase detector DET1P is coupled to the inputsignal VLF. An output of phase detector DET1P provides an output signalVout1PD that is indicative of the phase relationship at the fundamentalfrequency of which the motion, displacement, or deflection of the MEMSdevice is being compared with the input signal. To measure the staticphase and or time varying phase characteristic of the MEMS device at aharmonic (e.g., 2nd harmonic or Nth harmonic) frequency of input signalVLF, the output of Filter2 is coupled to a first input terminal of phasedetector, DET2P (e.g., block 112) and a second input terminal of phasedetector DET2P is coupled to the input signal VLF or a signal related tothe second harmonic frequency (or Nth harmonic) of VLF, which includesthe signal VLF′. An output of phase detector DET2P provides an outputsignal Vout2PD that is indicative of the phase relationship at thesecond harmonic frequency or Nth harmonic frequency of which the MEMSdevice driving or displacing at compared to the input signal VLF or to asignal related to an Nth harmonic of input signal VLF. With an optionalFilter3, to measure the static phase and or time varying phasecharacteristic of the MEMS device at a harmonic (e.g., 3rd harmonic orNth harmonic) frequency of input signal VLF, the output of Filter3 iscoupled to a first input terminal of phase detector, DET3P (e.g., block113) and a second input terminal of phase detector DET3P is coupled tothe input signal VLF or a signal related to the third harmonic frequency(or Nth harmonic) of VLF, which includes the signal VLF″. An output ofphase detector DET3P provides an output signal Vout3PD that isindicative of the phase relationship at the third harmonic frequency orNth harmonic frequency of which the MEMS device driving or displacing atcompared to the input signal VLF or to a signal related to an Nthharmonic of input signal VLF.

FIG. 5A shows an example top waveform from Vout104 wherein the bottomwaveform is an example VLF input signal sinusoidal waveform. Thedistortion from the top waveform example, which resembles a periodicparabolic signal, includes significant amounts of second and third orderdistortions (e.g., signals of twice and three times the fundamentalfrequency of the input signal VLF which is displaced on the bottom traceof FIG. 5A) in other order of >10% second harmonic and or >10% thirdharmonic distortion. To analyze this distorted waveform example that isindicative of non-linear displacement characteristics of a MEMS device,this distorted waveform may be coupled to a spectrum analyzer or an FFT(Fast Fourier Transform) for measuring the amounts of second, third, andor Nth harmonic distortion signals. The FFT may also include phaseinformation pertaining to the spectral analysis of the fundamentalfrequency signal, second harmonic signal, and or Nth harmonic signalfrom the distorted waveform and its input signal (e.g., VLF). Thewaveform of FIG. 5A may be analyzed in real time as function of time forthe amplitude and phase measurements for the spectrally decomposedsignal components. For example, in FIG. 4A by using a filter bank thatincludes one or more band pass filters, the amplitude level (oramplitude modulation) and or phase variation (or phase modulation) ofthe fundamental frequency and or harmonic distortion signal(s) can bemeasured as a function of time (e.g., logged or displayed as a timedomain waveform).

FIG. 6A shows an example circuit for block 104 from FIG. 4. Block 104includes a high frequency band pass filter for pass through signals atfrequency of VHF while preferably attenuating signals of otherfrequencies such as signals related to VLF, the low frequency inputsignal. The high frequency band pass filter includes a resonant circuitcomprising C1 and L1, and the input signal is coupled to this highfrequency band pass filter via R1 and C0. Since the input signal to R1is typically an amplitude modulated signal due to changing capacitancesof the MEMS device via input signal VLF, demodulation of the signal fromthe band pass filter C1 and L1 is done via coupling C1 and L1 to aninput terminal of amplifier A10, which isolates C1 and L1 from loadingeffects of Det104 and R2 that would affect the quality factor orbandwidth of the band pass filter (L1 and C1). The output of A1 thendrives the AM (amplitude modulation) detector/demodulator circuitcomprising diode or envelope detector Det104 with R2, C2 that forms apeak hold and discharging circuit. The charge capacitor C2 is coupled toan input of an optional low pass filter (e.g., to remove or attenuatesignals related to signal VHF, for example a 50 kHz low pass filter) isprovided by R3 and C3. The output of the optional low pass filter at C3is coupled to amplifier A11 to provide an AM demodulated signal thatprovides a signal indicative of amplitude variations or displacementvariations that may include distortion(s) caused by the MEMS device as afunction of time.

FIG. 7A shows a low frequency band pass filter circuit (block 105, 106,and or 107) for example for passing signals at the VLF signal frequencyand or a harmonic frequency of the VLF signal. Input resistor R31 iscoupled to a band pass filter that comprises C31 and L31 to form aresonant band pass filter. Although the inductor L31 can be a coil forexample such as a 0.1 Henry to 1.0 Henry inductor, or L31 can besubstituted with a gyrator, active inductor, or simulated inductorcircuit including an amplifier and a capacitor. The output of the lowfrequency band pass filter at L31 and or C31 is coupled to an input ofamplifier A31. The output of amplifier A31 provides an output signal.For example, the output signal from amplifier A31 is coupled to an AMdetector and or a phase detector.

FIG. 7A also shows an example amplitude detector or amplitude modulationdetector whose input signal In_′ is provided via the output of a lowfrequency band pass filter (e.g., via an output signal from A31 or via asignal from the output of block 105, 106, and or 107). A detector diodeD41 with R42 and C42 form an envelope detector to provide a signalindicative of the amplitude from one or more of the low frequency bandpass filters, block(s) 105, 106, and or 107. An optional low pass filterfrom the low frequency amplitude detector D41 may be included toattenuate signals whose frequency is related to the input signal VLF. Anoptional amplifier A41 provides the output signal of the low frequencyamplitude detector that includes a DC signal and or an AC signal,wherein the AC signal from Vout AM is indicative of amplitudefluctuations caused by fluctuations in the displacement of the MEMSdevice. Fluctuations in the displacement of the MEMS device or amicroactuator may include modulating (e.g., amplitude modulation and orphase modulation) one or more signals whose frequency is of afundamental frequency of the VLF input signal; or fluctuations in thedisplacement of the MEMS device or a microactuator may includemodulating (e.g., amplitude modulation and or phase modulation) one ormore signals whose frequency is of a harmonic frequency of the VLFsignal.

FIG. 8A shows an example phase detector for blocks 111, 112, and or 113from FIG. 4A. In FIG. 8A, an input signal, In′, such as Vout1 or Vout2or Vout3 is coupled to an input, Vi_ph, of an optional phase shiftercircuit, block 171, whose output signal Vo ph is coupled to an inputterminal, Vi_1, of a limiter circuit that removes or substantiallyremoves amplitude modulation that may be present in the input signal,In′. For a phase detector that includes a multiplier circuit such asblock 173, any amplitude variation of a signal into the multipliercircuit or phase detector circuit (e.g., Vi1_PD) will provide erroneousa signal at the output of the multiplier (e.g., Vo_PD). Thus at theoutput signal, Vo_1 of limiter circuit 172, there is essentially noamplitude variation. An example limiter circuit may include a comparatorcircuit and or one or more stages of amplification. A reference signalsuch as the low frequency generator input signal, VLF, VLF′, or VLF″ asshown in FIG. 4A, is coupled to a second input terminal, Vi2_PD of thephase detector 173. An output signal, Vo_PD, from block 173 phasedetector is then coupled to a filter, 174, which removes signals whosefrequency is related to VLF. Filter block 174 may include a low passfilter or filter that removes signal components related to thefundamental frequency of VLF and or that removes signal componentsrelated to one or more harmonic frequency of VLF. The output signal fromthe filter 174, VoutPD provides a signal indicative of a phasedifference between the input signal VLF and one or more signal(s) fromthe demodulator/detector block 104. For example, VoutPD provides a phasesignal indicative the phase difference between input signal VLF and thefundamental frequency signal related to the displacement of the MEMSdevice. Alternatively, VoutPD may provide a signal indicative the phasedifference between input signal VLF and a harmonic frequency signalrelated to the displacement of the MEMS device.

For example, FIG. 8A shows an example of a first low frequency phasedetector, a second low frequency phase detector, and or an Nth lowfrequency phase detector.

In FIG. 8A each sub-block such as 171, 172, 173, and or 174 may includerespectively a first or Nth phase shifting circuit or phase shifter(171), a first or Nth limiter circuit (172), a first or Nth phasedetector circuit, and or a first or Nth phase detector filter.

Alternatively, in FIG. 8A each sub-block such as 171, 172, 173, and or174 may include respectively a fundamental frequency or Nth harmonicfrequency phase shifting circuit or phase shifter (171), a fundamentalfrequency or Nth harmonic limiter circuit (172), a fundamental frequencyor Nth harmonic phase detector circuit, and or fundamental frequency orNth harmonic phase detector filter.

In another embodiment FIG. 8A shows an example of a fundamentalfrequency low frequency phase detector, a second harmonic low frequencyphase detector, and or an Nth harmonic low frequency phase detector.

FIG. 9A shows another embodiment to adjusting the frequency of anoscillator, 505, (e.g., more precisely) including a phase detector, 506.This oscillator in one example is used to drive a MEMS device atresonance, wherein the resonant frequency of the MEMS device (ormicroactuator) 502, a peak amplitude response is achieved. However,identifying the peak amplitude response of the MEMS device is difficultto identify since even a slightly off resonant frequency will havealmost the same peak amplitude when compared to the peak amplitude atthe resonant frequency. A phase detector is used to precisely identifythe peak resonant response of the MEMS device. Generally, at resonancethe MEMS device exhibits a 0 degrees when frequencies below and abovethe resonance frequency have phase shifts of +90 degrees and −90degrees. If a MEMS device at resonance has a 90 degrees phase shift, thephase shifts are 0 degrees and −31 180 degrees for frequencies below andabove the resonance frequency. In FIG. 9A, a MEMS device 502 is coupledto a bias DC signal VDC, a low frequency signal VLF1 (e.g., a lowfrequency sine wave signal), and a high frequency signal VHF viacombiner circuit 501. The capacitance current from C_MEMS, 502, isconverted to a voltage signal via a first amplifier 503 (e.g., firstamplifier 503 may include a trans-resistance amplifier or an amplifier).The output of first amplifier 503 is coupled to an input terminal (e.g.,via block 504) of a band pass filter to pass a signal whose frequency isat or near the frequency of signal VHF (e.g., a high frequency signal).An output terminal of the band pass filter is then coupled to an inputof a detector or a demodulator (e.g., Det 504 that may include anamplitude modulation (AM) detector such as an envelope detector) torecover a (e.g., low frequency) signal related to the input signal VLF1.An output of the AM detector may be coupled to a detector filter thatmay include a low pass filter, band pass filter, and or band rejectfilter. An output signal, Vout504, is provided from the detector and ordetector filter. A first input terminal (e.g., InA of 506) of phasedetector 506 is coupled to the output of a voltage controlled oscillator(505) signal VLF1. The output of the voltage controlled oscillator 505is coupled to a first input terminal of the combiner 501. A secondterminal of the phase detector (e.g., InB of 506) is coupled to Vout504,the output of the AM detector or detector filter in block 504. An outputsignal, Vout1PD from the phase detector 506 is coupled to a secondamplifier 507, which may include an amplifier with a low pass filtereffect or amplifier 507 with an integrating function (e.g., anintegrator amplifier 507 including integrating capacitor C1 and orincluding input resistor R1). An output of amplifier 507 is coupled to avoltage control input terminal of a voltage controlled oscillator 505(e.g., voltage controlled oscillator=VCO), which is noted as VLF VCO forblock 505. The phase lock feedback system shown in FIG. 9A includes areference voltage, Vph_ref, coupled to an input of amplifier 507 (e.g.,a non inverting input or (+) input of amplifier 507) that results in thephase lock feedback system to vary the frequency of the voltagecontrolled oscillator 505 until the output voltage, Vout1PD from phasedetector 506 matches the reference voltage, Vph_ref For example, if thephase detector provides 0 volts when the MEMS device is at its resonantfrequency, Vph_ref can be set to 0 volts. Or in general if the phasedetector provides “X” volts when the MEMS device is at its resonantfrequency, Vph_ref can be set to “X” volts.

To determine or identify the peak displacement amplitude response of theMEMS device as a function of the frequency of signal VLF1, the frequencyof VLF1 is varied until the peak amplitude response is determined viausing a phase detector 506.

In another embodiment by setting the phase reference voltage, Vph_ref,the voltage controlled oscillator can be set to a frequency within theband pass characteristic of the MEMS or microactuator. For example, ifthe phase characteristic of a MEMS devices is in a range of 0 degrees to180 degrees with 90 degrees at resonance (e.g., peak amplitude), an asan example the phase detection range relates 0 degrees to a voltage V1and a voltage of V2 for 90 degrees, and a voltage of V3 for 180 degrees,then Vph_ref can be set to V2 +/−ΔV=Vph_ref. For example Vph_ref can beset such that the MEMS device is driven with a frequency that is plus orminus “Y” degrees from the resonant frequency. For example, by settingVpf_ref to a predetermined value, the MEMS device can be driven at afrequency below or above the resonant frequency (e.g., at either of the−3 dB frequency, or at 45 degrees or 135 degrees where 90 degrees is atresonance). In another embodiment, the reference phase voltage, Vph_refmay be varied or time varying to measure phase and amplitude response ofthe MEMS via varying the frequency of the voltage controlled oscillatoras a function of phase between the low frequency input signal and thephase output response of the MEMS device.

Electromechanical systems can also include a “sub-mode” whereby theelectromechanical system resonates at a lower amplitude level (e.g.,lower displacement) when compared to its dominant resonant frequencywith the largest amplitude (e.g., frequency with the largest amplitudedisplacement). In FIG. 10 an amplitude versus frequency plot shows anexample of a mechanical device or MEMS device that has a dominantresonant frequency at F1; and FIG. 10A shows that there is also at leastone sub-mode resonant frequency at F2 and or F3, in which each has asmaller amplitude response that when the MEMS device is operating at F1.

By using a filter or filter bank (e.g., as shown in FIG. 4A), a MEMS orelectromechanical device can be analyzed at a “sub-mode” frequency foramplitude and or phase variation/modulation in real time. Thus, oneobject of the invention is to measure the electromechanical system interms of amplitude and phase at the sub-mode frequency and or at leastone harmonic of the sub-mode frequency. For example the system shown inFIG. 4A may be used to measure an amplitude and or a phase of a MEMS (ormicroactuator device) at one or more harmonic of a sub-mode frequencyvia one or more filters or via a filter bank. The amplitude measurementmay include a static measurement of amplitude and or may include adynamic measurement of amplitude (e.g., amplitude modulation measurementof a harmonic signal of a sub- mode frequency; or a static amplitudemeasurement such as an average over a time period of an amplitude of aharmonic signal of a sub-mode frequency).

Additional aspects of the disclosure are directed to providemeasurements as a function of time for the amplitude and phase at one ormore sub-mode frequency. For example the system shown in FIG. 4A may beused to measure an amplitude and or a phase of a MEMS (or microactuatordevice) of a sub-mode frequency via one or more filters or via a filterbank. The amplitude measurement may include a static measurement ofamplitude and or may include a dynamic measurement of amplitude (e.g.,amplitude modulation measurement of a sub-mode frequency; or a staticamplitude measurement such as an average over a time period of anamplitude of a sub-mode frequency).

One embodiment may include a system for measuring dynamic distortion,modulation distortion, modulation in terms of amplitude variation and orphase variation of a MEMS or microactuator with one or more inputsignals.

For example the MEMS or microactuator may be measured for amplitudemodulation and or phase modulation related to displacement or deflectioncharacteristic of the MEMS device or microactuator in a followingmanner: Coupling a first signal and a second signal to a first terminalof the MEMS device or microactuator to induce deflection or displacementof the MEMS device or microactuator, wherein the frequency of the secondsignal is higher than the frequency of the first signal; coupling anelectrical signal, a MEMS capacitance signal, from the MEMS device ormicroactuator that is indicative of capacitance of the MEMS device ormicroactuator; coupling the MEMS capacitance signal to a firstdemodulator to demodulate the MEMS capacitance signal whose frequency isat a frequency of the frequency of the second signal; providing ademodulated signal from the first demodulator wherein the demodulatedsignal includes one or more signals with frequency or frequenciesrelated to the first signal that may include frequency or frequencies ofthe fundamental and or harmonic of the first signal; coupling thedemodulated signal from the first demodulator to a spectrum analyzer, toa FFT (Fast Fourier Transform), to an input terminal of a seconddemodulator, and or to a first input terminal of a third demodulator;wherein the second demodulator includes an amplitude modulation detectorand or the third demodulator includes a phase modulation detector;wherein the third demodulator includes a second input terminal that iscoupled to the first signal; and wherein the second demodulator providesa demodulated signal indicative of amplitude modulation of displacementor deflection of the MEMS or microactuator, and or wherein the thirddemodulator provides a demodulated signals indicative of phasemodulation of displacement or deflection of the MEMS or microactuator.The first signal and second signal may include a first signal generatorand a second signal generator; the first or second signal generator mayinclude a voltage controlled oscillator for providing a frequencymodulated signal; the first demodulator may be any combination of anamplitude modulation detector/demodulator, a phase detector/demodulator,or a frequency modulation detector/demodulator. Another embodiment mayfurther comprise a band pass filter coupled between an output terminalfirst demodulator and an input terminal of the second demodulatorwherein the band pass filter pass frequencies related to the fundamentalfrequency or a harmonic of the first signal.

Various aspects may be implemented using and/or in connection withembodiments disclosed in U.S. Provisional Patent Application Ser. No.62/627,613, entitled “Signal Driving and Measuring Capacitors and orNonlinear Elements,” to which priority is claimed and which is fullyincorporated herein by reference. For instance, various embodiments aredirected to a method and/or an apparatus comprising elements inaccordance with the Specification of the '613 Provisional PatentApplication and as characterized with the figures therein.

Various aspects may also be implemented using and/or in connection withembodiments disclosed in U.S. Provisional Patent Application Ser. No.62/745,118, entitled “Apparatus for Monitoring the Position of anElectrostatically Driven Resonator and Method Therefor,” to whichpriority is claimed and which is fully incorporated herein by reference.For instance, various embodiments are directed to an apparatuscomprising elements in accordance with the Specification of the '118Provisional Patent Application and the description in Appendices A and Btherein (each hereby incorporated by reference); one such embodimentincludes driving the micro-actuator via a first stator plate andreceiving a signal for processing or analysis via a second stator platewherein the middle or moving structure's electrical terminal is notused, and another such embodiment includes driving the micro-actuatorvia a first stator plate and receiving a signal for processing oranalysis via a second stator plate wherein the middle or movingstructure's electrical terminal is connected to one of the stator plates(e.g., the first or second stator plate); and yet another suchembodiment includes driving the micro-actuator via a first stator plateand receiving a signal for processing or analysis via the middle ormoving structure's electrical terminal, wherein the second statorplate's electrical terminal is not connected. Various embodiments aredirected to methods as carried out in accordance with the Specificationof the '118 Provisional Patent Application and the description inAppendices A and B therein.

One or more embodiments are directed to a system of measuring motion ordisplacement of a microactuator via providing a signal indicative ofchanges in capacitance of the microactuator that includes at least afirst terminal and a second terminal comprising: a first signalgenerator operating at a first frequency that outputs a first signal anda second signal generator operating at a second frequency that outputs asecond signal wherein the first frequency is lower than that of thesecond frequency. The first signal may be combined or added with thesecond signal to provide a composite signal. Various terminals may beimplemented as follows. The composite signal is coupled to the firstterminal of the microactuator, the second terminal of the microactuatoris coupled to an input of a first amplifier, an output of the firstamplifier is coupled to an input terminal of a first band pass filtercircuit wherein the first band pass filter circuit passes a signalrelated to the second frequency, an output terminal of the first bandpass filter circuit to an input terminal of an amplitude modulationdemodulator/detector; and an output terminal of the amplitude modulationdemodulator/detector is coupled to an input terminal of a filter bankwherein the filter bank includes a first low frequency filter andwherein the first low frequency filter includes an input terminal and anoutput terminal. The input terminal of the first low frequency filter iscoupled to the output terminal of the amplitude modulationdemodulator/detector. An output terminal of the first low frequencyfilter is coupled to a first terminal of a first low frequency phasedetector. A signal related to the first signal generator is coupled to asecond terminal of the first low frequency phase detector. A signal isoutput from and output terminal of the first low frequency phasedetector, in which the output signal of the first low frequency phasedetector is indicative of a phase modulation effect related to thedisplacement or motion of the microactuator.

In various implementations, an input of a second low frequency filter iscoupled to the output terminal of the amplitude modulationdemodulator/detector, and an output terminal of the second low frequencyfilter is coupled to a first terminal of a second low frequency phasedetector. A signal related to the first signal generator to a secondterminal of the second low frequency phase detector. A signal from anoutput terminal of the second low frequency phase detector is output,which is indicative of a phase modulation effect related to thedisplacement or motion of the microactuator, and wherein a frequency ofthe phase modulation effect includes a frequency related to a harmonicof the fundamental frequency of the first signal from the first signalgenerator.

In certain implementations, a fundamental frequency of the firstgenerator referenced above is substantially equal to a dominant modefrequency of the microactuator or wherein the fundamental frequency ofthe first generator is substantially equal to a sub-mode mode frequencyof the microactuator. In other implementations, the fundamentalfrequency of the first generator is substantially equal to a dominantmode frequency of the microactuator or wherein the fundamental frequencyof the first generator is substantially equal to a sub-mode modefrequency of the microactuator.

In certain implementation, a first limiter circuit is included with thefirst low frequency phase detector and/or a second limiter circuit isincluded with the second low frequency phase detector.

In some embodiments, an input terminal of a second harmonic signalamplitude detector is coupled to the output terminal of the first lowfrequency filter terminal, and an output of the second harmonic signalamplitude detector provides a signal indicative of second harmonicdisplacement of the microactuator or wherein an output of the secondharmonic signal amplitude detector provides a signal indicative ofsecond harmonic motion of the microactuator.

Another embodiment is directed to a system for adjusting an oscillatorto a resonant frequency of a microactuator via a feedback system. Thesystem includes a first signal generator that includes a voltagecontrolled oscillator circuit comprising a voltage control inputterminal to vary the frequency of the voltage controlled oscillator as afunction of voltage into the voltage controlled input terminal, furthercomprising the first signal generator includes an output terminal thatprovides an oscillating signal, and a second signal generator of asecond frequency that includes a second signal output terminal whereinthe first frequency is less than the second frequency. A combinerincludes a first input terminal, a second input terminal, and an outputterminal. The first signal output terminal is coupled to the first inputterminal of the combiner and coupling the second signal output terminalto the second input terminal of the combiner. The output terminal of thecombiner is coupled to an input terminal of a first amplifier. An outputof the first amplifier is coupled to an input of a first high frequencyband pass filter. An output of the first high frequency band pass filteris coupled to a first input terminal of a phase detector. The outputterminal of the voltage controlled oscillator is coupled to a secondinput terminal of the phase detector, and an output terminal of thephase detector is coupled to a first input terminal of a secondamplifier. A reference voltage is coupled to a second input terminal ofthe second amplifier, and an output terminal of the second amplifier iscoupled to the voltage control input terminal of the voltage controlledoscillator. The frequency voltage controlled oscillator output signal isadjusted to substantially a resonant frequency of the microactuator. Theresonant frequency of the microactuator may, for example, include adominant mode frequency or a sub-mode frequency.

Another embodiment is directed to a system for measuring amplitudemodulation and or phase modulation related to displacement or deflectioncharacteristic of the MEMS device or microactuator. A first signal and asecond signal are coupled to a first terminal of the MEMS device ormicroactuator to induce deflection or displacement of the MEMS device ormicroactuator, wherein the frequency of the second signal is higher thanthe frequency of the first signal. An electrical signal, a MEMScapacitance signal, is coupled from the MEMS device or microactuatorthat is indicative of capacitance of the MEMS device or microactuator.The MEMS capacitance signal is coupled to a first demodulator todemodulate the MEMS capacitance signal whose frequency is at a frequencyof the frequency of the second signal. A demodulated signal is producedfrom the first demodulator wherein the demodulated signal includes oneor more signals with frequency or frequencies related to the firstsignal that may include frequency or frequencies of the fundamental andor harmonic of the first signal. The demodulated signal from the firstdemodulator is coupled to a spectrum analyzer, to a FFT (Fast FourierTransform), to an input terminal of a second demodulator, and or to afirst input terminal of a third demodulator. The second demodulatorincludes an amplitude modulation detector and or the third demodulatorincludes a phase modulation detector. The third demodulator includes asecond input terminal that is coupled to the first signal. The seconddemodulator provides a demodulated signal indicative of amplitudemodulation of displacement or deflection of the MEMS or microactuator,and or wherein the third demodulator provides a demodulated signalsindicative of phase modulation of displacement or deflection of the MEMSor microactuator.

The system for measuring amplitude modulation and or phase modulationmay be implemented as follows. In some embodiments, the first or secondsignal generator includes a voltage controlled oscillator for providinga frequency modulated signal. The first demodulator may be anycombination of an amplitude modulation detector/demodulator, a phasedetector/demodulator, or a frequency modulation detector/demodulator,and may include a frequency modulation detector/demodulator. A band passfilter may be coupled between an output terminal first demodulator andan input terminal of the second demodulator, wherein the band passfilter pass frequencies related to the fundamental frequency of thefirst signal. A band pass filter may be coupled between an outputterminal first demodulator and an input terminal of the seconddemodulator wherein the band pass filter pass frequencies related to aharmonic frequency of the first signal.

This disclosure is illustrative and not limiting; further modificationswill be apparent to one skilled in the art and are intended to fallwithin the scope of the appended claims and or of the embodimentsdescribed. For instance, various embodiments discussed as beingimplemented separately can be implemented together, and portions ofdiscussed embodiments may be implemented separately. In this context,the various figures provided herewith may be implemented together, anddifferent components within individual figures may be implementedseparately. Moreover, various embodiments may involve thosecharacterized in the underlying provisional applications to whichpriority is claimed and are fully incorporated herein by reference.

Terms to exemplify orientation, such as upper/lower, left/right,top/bottom and above/below, may be used herein to refer to relativepositions of elements as shown in the figures. It should be understoodthat the terminology is used for notational convenience only and that inactual use the disclosed structures may be oriented different from theorientation shown in the figures. Thus, the terms should not beconstrued in a limiting manner.

The skilled artisan would recognize that various terminology as used inthe Specification (including claims) connote a plain meaning in the artunless otherwise indicated. As examples, the Specification describesand/or illustrates aspects useful for implementing the claimeddisclosure by way of various circuits or circuitry which may beillustrated as or using terms such as blocks, modules, device, system,unit, controller, function(s) and/or other circuit-type depictions(e.g., reference numerals 603 and 604 of FIG. 11 depicts a block/moduleas described herein). Such circuits or circuitry are used together withother elements to exemplify how certain embodiments may be carried outin the form or structures, steps, functions, operations, activities,etc. For example, in certain of the above-discussed embodiments, one ormore modules are discrete logic circuits or programmable logic circuitsconfigured and arranged for implementing these operations/activities.Depending on the application, the instructions (and/or configurationdata) can be configured for implementation in logic circuitry, with theinstructions (whether characterized in the form of object code, firmwareor software) stored in and accessible from a memory (circuit). Asanother example, where the Specification may make reference to a “first[type of structure]”, a “second [type of structure]”, etc., where the[type of structure] might be replaced with terms such as [“circuit”,“circuitry”, “function” and others], the adjectives “first” and “second”are not used to connote any description of the structure or to provideany substantive meaning; rather, such adjectives are merely used forEnglish-language antecedence to differentiate one such similarly-namedstructure from another similarly-named structure (e.g., “first circuitconfigured to convert . . . ” is interpreted as “circuit configured toconvert . . . ”).

Based upon the above discussion and illustrations, those skilled in theart will readily recognize that various modifications and changes may bemade to the various embodiments without strictly following the exemplaryembodiments and applications illustrated and described herein. Forexample, methods as exemplified in the Figures may involve steps carriedout in various orders, with one or more aspects of the embodimentsherein retained, or may involve fewer or more steps. Such modificationsdo not depart from the true spirit and scope of various aspects of thedisclosure, including aspects set forth in the claims.

What is claimed is:
 1. A method for use with a MEMS apparatus, themethod comprising: actuating the MEMS apparatus via an input signal,wherein the MEMS apparatus has an arrangement of at least onemicro-mirror that is integrated with a capacitive portion and thatprovides a field of view; using modulation circuitry to modulate theinput signal via signal modulation selected as including one or acombination from among the following: drive amplitude modulation, phasemodulation, and frequency modulation; and using the modulated inputsignal to drive the MEMS apparatus and to cause a change or increase inthe field of view provided by the arrangement of at least onemicro-mirror.
 2. The method of claim 1, further including using the MEMSapparatus for scanning with a configurable field of view facilitated viathe modulated input signal driving the MEMS apparatus.
 3. The method ofclaim 1, wherein the signal modulation includes drive amplitudemodulation.
 4. The method of claim 1, wherein the signal modulationincludes phase modulation.
 5. The method of claim 1, wherein the signalmodulation includes frequency modulation.
 6. The method of claim 1,wherein the signal modulation includes two of the following: driveamplitude modulation, phase modulation, and frequency modulation.
 7. Anapparatus including first terminal, a common terminal, and a secondterminal, the apparatus comprising: first circuitry to: combine a firstdriving signal with a first high frequency signal coupled to a firstterminal, wherein the frequency of the first high frequency signal ishigher than the frequency of the first driving signal; and combine asecond driving signal with a second high frequency signal coupled to thesecond terminal, wherein the frequency of the second high frequencysignal is higher than the frequency of the second driving signal; athird terminal to receive an output signal from the first circuitry; andsecond circuity having an input terminal coupled to receive the outputsignal from the first circuitry, and further having an output terminalto provide a signal indicative of capacitance change or motion, whereinthe second circuity includes at least one of an amplitude detector and afirst phase detector.
 8. The apparatus of claim 7, further comprisingthe frequency of the first high frequency signal is substantially thesame frequency as the frequency of the second high frequency signal. 9.The apparatus of claim 8, further including that the phase of the firsthigh frequency signal is not equal to the phase of the second highfrequency signal.
 10. The apparatus of claim 9, further comprising thephase of the first high frequency signal is different in phase of thesecond high frequency signal by a 90 degree difference.
 11. Theapparatus of claim 7, further comprising the first high frequency signalincludes an IN-Phase signal and the second high frequency signalincludes a Quadrature Phase signal.
 12. The apparatus of claim 7,further include the phase detector includes a second input terminal. 13.The apparatus of claim 12, further includes coupling a reference signalto the second input terminal of the phase detector.
 14. An apparatusproviding one or more signals indicative of a device having a firstterminal, a common terminal, and a second terminal comprising: a firstdriving signal combined with a first high frequency signal coupled tothe first terminal wherein the frequency of the first high frequencysignal is higher than the frequency of the first driving signal; asecond driving signal combined with a second high frequency signalcoupled to the second terminal wherein the frequency of the second highfrequency signal is higher than the frequency of the second drivingsignal; a third terminal of the device coupled to an input terminal of afirst phase detector and/or; a third terminal of the device coupled toan input terminal of a second phase detector; and wherein a signalindicative of capacitance change or motion from the device is providedvia an output terminal of the first phase detector and/or an outputterminal from the second phase detector.
 15. The apparatus of claim 14,further comprising the frequency of the first high frequency signal issubstantially the same frequency as the frequency of the second highfrequency signal.
 16. The apparatus of claim 14, further including thatthe phase of the first high frequency signal is not equal to the phaseof the second high frequency signal.
 17. The apparatus of claim 16,further comprising the phase of the first high frequency signal isdifferent in phase of the second high frequency signal by a 90 degreedifference.
 18. The apparatus of claim 14, further comprising the firsthigh frequency signal includes an IN-Phase signal and the second highfrequency signal includes a Quadrature Phase signal.
 19. The apparatusof claim 14, wherein the first phase detector includes a second inputterminal and/or the second phase detector includes a second inputterminal.
 20. The apparatus of claim 19, further including coupling afirst reference signal to the second input terminal of the first phasedetector and/or coupling a second reference signal to the second inputterminal of the second phase detector.
 21. The apparatus of claim 14,further comprising providing a first signal indicative of capacitance ormovement of the device from the first terminal and/or providing a secondsignal indicative of capacitance or movement of the device from thesecond terminal.
 22. An apparatus to measure time varying distortionfrom a MEMS device, the MEMS device including a first terminal and asecond terminal, wherein the first terminal of the MEMS device isrelated to a first plate of the MEMS device comprising: coupling a firstdriving signal with a frequency of fmod and a first high frequencysignal to the first terminal of the MEMS device; coupling the secondterminal of the MEMS device to an input terminal of a first demodulatorcircuit; and coupling an output terminal of the first demodulatorcircuit to any combination of: an input terminal of a first filter, aninput terminal of a second filter, an input terminal of an Nth filtercircuit, or to a filter bank; wherein the first filter, second filter,Nth filter, or filter bank passes a signal whose frequency issubstantially fmod or a multiple of fmod and further comprising; anoutput terminal of the first filter, second filter, Nth filter, orfilter bank provides a signal indicative of time varying distortion fromvarying capacitance of the MEMS or from movement of the MEMS.
 23. Theapparatus of claim 22, further comprising the time varying distortionincludes time varying harmonic distortion.
 24. The apparatus of claim22, further comprising the MEMS device having more than onedimension/axis, and wherein the first terminal of the MEMS device isassociated to a first dimension/axis, and wherein a third terminal ofthe MEMS device is associated with a second dimension/axis of the MEMSdevice.
 25. The apparatus of claim 24, wherein a second driving signalwith a frequency of f_(mod2) is coupled to the third terminal of theMEMS device.
 26. The apparatus of claim 22, wherein the time varyingdistortion includes time varying intermodulation distortion.
 27. Theapparatus of claim 26, further comprising the time varyingintermodulation signal includes a frequency characterized in the form of(p×f_(mod)±q×f_(mod2)), wherein p and q are integers.
 28. The apparatusof claim 22, wherein the output terminal first filter passes signalswhose frequency is fmod and wherein the output terminal second filterpasses signals whose frequency is a multiple or a harmonic of f_(mod2),further comprising; coupling the output terminal of the first filter toan input terminal of a first phase detector and/or coupling the outputterminal of the second filter to an input terminal of a second phasedetector wherein a signal from an output terminal of the first phasedetector and a signal from an output terminal of the second phasedetector provides an indication of phase difference or phase modulationbetween the signals from the output terminals of the first and secondphase detectors.
 29. An apparatus to provide a driving signal to a MEMSdevice comprising: a MEMS device with a first terminal and a secondterminal; the second terminal of the MEMS device is coupled to an inputterminal of a detector circuit and wherein the detector circuit includesan output terminal; the output terminal of the detector circuit iscoupled to a first input terminal of a combining circuit wherein thecombining circuit includes a second input terminal and the combiningcircuit includes an output terminal; coupling the drive signal to thesecond terminal of the combining circuit; and coupling the outputterminal of the combining circuit to the first terminal of the MEMSdevice.
 30. The apparatus of claim 29, further including a feedbacksystem or feedback circuit.
 31. The apparatus of claim 29, furtherincluding adding a first high frequency signal to the first terminal ofthe MEMS device.
 32. The apparatus of claim 31, wherein the detectorcircuit is responsive to the high frequency signal.
 33. The apparatus ofclaim 32, wherein the detector circuit includes an amplitude modulationsignal detector.
 34. The apparatus of claim 32, wherein the detectorcircuit includes a phase shifting circuit, a first squaring circuit, asecond squaring circuit, and a summed squared circuit/function.
 35. Theapparatus of claim 34, further comprising a square rootcircuit/function.
 36. An apparatus for driving a MEMS device, the MEMSdevice having a first terminal and a second terminal; and a first highfrequency signal source comprising: coupling the second terminal of theMEMS device to an input terminal of a first filter/detector circuit,wherein the first filter/detector circuit includes an output terminal,further comprising; a phase detector including a first input terminal, asecond input terminal, and an output terminal; coupling the outputterminal of the filter/detector circuit to the second input terminal ofthe phase detector; coupling the output terminal of the phase detectorto a control input terminal of a voltage controlled oscillator whereinthe voltage controlled oscillator includes an output terminal; couplingthe output terminal of the voltage controlled oscillator to the firstinput terminal of the phase detector further comprising; a combiningcircuit having a first input terminal, a second input terminal, and anoutput terminal; coupling the first high frequency signal source to thefirst input terminal of the combining circuit; further coupling theoutput terminal of the voltage controlled oscillator to the second inputterminal of the combining circuit; and coupling the output terminal ofthe combining circuit to the first terminal of the MEMS device.
 37. Theapparatus of claim 36, wherein the combining circuit includes a thirdinput terminal.
 38. The apparatus of claim 37, further includingcoupling a DC source to the third input terminal of the combiningcircuit.